I'm requesting for recommendations for games that stand out from the rest in their genre, and not in the sense of being the best game in that niche but actually bringing something new and innovative to the table. I've not had much experience in gaming, but I have a few games to give you a hint on what I am talking about:
Superhot: Time only moves when you do
Viewfinder: Convert 2D pictures seamlessly into interactive 3D environments
Superliminal: Change size of objects by working with perception
Portal: Portals
Scribblenauts: Summon objects by describing them in a notepad
I am not focused on the story, no. of hours of playtime, date of release or its popularity. It just needs to be playable and be enjoyable (and be available in PC).
Majesty (Majesty 2 is okay, but lacks the charm of the original, but YMMV) - you run a kingdom full of heroes. The catch? You don't command the heroes. They have their own AI and goals and you have to offer incentives and place the necessary buildings appropriately to both enable and encourage them to do their jobs of saving the kingdom.
Ronin - a stealth/platformer. Combat is turn-based. No, combat is not mechanically separate from the stealth OR the platforming. Relatively short but very fascinating.
Pawnbarian - Roguelike, but movement and combat is done by chess rules.
Exanima. Combat is based entirely around physics/momentum and positioning. It's hard to get the hang of, but is immensely satisfying once you get your "He's starting to believe" Matrix moment and successfully block a few attacks in a row.
Crusader Kings 3. You know those map-painting Grand Strategy games, where the goal is to conquer other territories? One of those, but you're running a noble dynasty whose fortunes rise and fall, even passing between the overlordship of different countries and kingdoms. A lot of personality. I guess it's not as innovative as it once was, since it's spawned imitators at this point. Hm.
Ring of Pain. It's... hard to describe.
Phasmophobia. Multiplayer only. You hunt ghosts. Not like, 'combat' hunt ghosts, like 'You need to find evidence of ghosts' hunt ghosts. But the ghosts definitely hunt you back - in a much more malicious way.
Death Stranding. Walking simulator. No, not like 'You don't do anything but hold down the walk button', like 'You need to keep your balance while carrying things' walking simulator. Immensely weird.
Star Trek: Bridge Crew. Multiplayer only (at least practically speaking). Each person plays a separate member of the titular bridge crew, and cooperation to achieve even simple tasks is key.
Gods Will Be Watching. A series of puzzle scenarios about calculated risk, failure, and learning the rules anew each time.
Tunic is incredibly unique and I can't say I've played anything like it. On the surface it's a classic dungeon crawler zelda inspired thing, but once you play.... Really any amount of it, you start to see past the veil and the real game is revealed to you. Even after completing the entire game and all achievements, there is technically more of the game available to be explored.
Outer Wilds (not to be confused with Obsidian's Outer Worlds) will be an absolute bliss for anyone who enjoyed portal or superliminal. It may be the single greatest puzzle/exploration game ever made, with no exaggeration.
Return of the Obra Dinn was a game that I could not put down. I played it in one sitting beginning to end. I was enthralled and I felt like Sherlock fucking Holmes. It is a very unassuming game but by God, you will be gripped. It stands up there with Outer Wilds as being a game that absolutely propelled itsself up to one of the best of its genre (this one being Mystery/Puzzle)
Fez: a 2D plateformer in which you can change the perspective to create ways to unreachable plateforms
Baba Is You: a puzzle game in which you move blocks with words written on them, combining them to create small phrases which become new rules of the game.
Impossible Creatures - an RTS where you slurp up DNA from local wildlife and use that to create weird hybrids of multiple animals, then produce those as units that you control to complete missions. Great concept but I think it ended up being a bit unbalanced.
Papers Please - pretty unique gameplay in that you had to literally read through paperwork and approve/reject people at a border crossing. Good social commentary.
Katamari Damacy - The objective is to roll a ball-like thing called a katamari, to roll up objects, and make the katamari bigger and bigger. You can roll up anything from paper clips and snacks in the house, to telephone poles and buildings in the town, to even living creatures such as people and animals. Once the katamari is complete, it will turn into a star that colors the night sky. Sounds weird, but it's super fun, trust me. Plus, it's soundtrack is kickass.
Factorio - its a logistics rts but the pollution mechanic is different. Instead of just gather resources to build things which build bigger things, you also make pollution as a side effect. This feeds the native monsters and also evolves them. Managing your pollution cloud is a strategy. That or build massive defensives for when they come to eat you.
Maybe Antichamber? It‘s a first-person puzzle game like Portal, but based on the idea of the „rooms“ changing as you go through them, so each room basically has its own mechanic to figure out
Faster than light - manage crew in a 2D strategy environment and jump around in space. Pretty unique gameplay which only recently got some clones.
Teardown - Work as criminal stealing stuff, but the clue is you can destroy everything and you need to create smart parkour to steal stuff right in time before the cops arrive. Also you can sandbox play it if you get bored.
Terra Nil - Bring back nature to a destroyed earth, with relaxing and calm mechanics. Highly recommend.
Others: FEZ, solve puzzles. Deep Rock Galactic, because dwarfs being this much dwarf is just dwarftastic. Rock and Stone!
Wow. I'm super impressed with all the suggestions here. I'll add a few of my own that haven't been mentioned yet.
Her Story - you query a police archive database for video clips, eventually revealing the plot. Kind of a mash between a murder mystery book with the pages out of order and Google. If you like it, check out Immortality
What Remains of Edith Finch - all you can do is walk around a very unusual house. The narrative reveals itself as you do so. That narrative is fantastical and heartbreaking and also very sweet.
Crawl - multiplayer game - you are all trying to escape a monster and trap filled dungeon. One of you is alive and the rest are spirits who can possess the monsters and traps. Any time a spirit kills the living player, they become the living player. Unique boss fight at the end where multiple spirits control parts of a huge boss monster.
In Return of the Obra Dinn you play an insurance claims investigator. You can magically view the moment of somebody's death and hear the audio prior to it to aid in your investigation of a ghost ship.
I've never played such a unique big budget game. The core mechanic is terrain traversal to make deliveries, and the game continues to give you tools throughout it to accomplish that.
Cultist Simulator is pretty unique... not necessarily in a good way. It's a storytelling/puzzle game with some great writing if you can power your way through the gameplay. The mechanics are deliberately very obtuse, with no tutorial, to emulate the fact that diving into the occult is confusing and dangerous. The end result is that the game is very unique and cool, but it's absolutely not for everyone. TL;DR on the basic mechanics: you have a handful of verb boxes, such as Talk or Research, as well as various cards that you can slot into them. Each card has a variety of tags on it. Depending on which cards with which tags you put into the various verb boxes, you get different results.
You play a space archaeologist, and the big central mechanic of the game is translating things written in the Ancient language.
Ancient is written using ideographs, and more complex ideas are represented by combining glyphs that describe the concept, like ever more complex compound words. There are art of speech markers, glyphs that describe how other glyphs in a word relate to each other, intensifiers, and even a few cases where super common words are just the combination of other basic glyphs into a single composite like a Norse bindrune (for example the symbols for creature and knowledge overlap to make person, an intelligent creature). 46 base ideographs, but that includes digits, so it's only 10 more than English.
So for example, a word that reads NOUN-person-Sub/Obj CONNECTOR-NOUN-knowledge-person means "Emperor", because noun-knowledge-person means "law" and thus the result is a person who the law belongs to, aka a ruler or in the context of an empire the emperor. Replace that noun marker glyph at the beginning with the adjective marker glyph and you would have "imperial", the quality of being emperor-like.
One of the longest words to appear in the game translates as "mouse" and it's 21 letters long and is literally something like creature-CONNECTOR-many-many-Sub/Obj CONNECTOR-ADJECTIVE-NOT-ADJECTIVE-CONNECTOR-many-creature-CONNECTOR-ADJECTIVE-ABSTRACT NOUN-person-CONNECTOR-light-NOUN-plant-CONNECTOR-rock, which is several words stitched into a compound word, where some of those words are themselves compound words (the idea is something like "creature like a very small pig", but the word I'm calling "pig" means "creature that is happy in the soil" where happy is something like "the quality of a person who is metaphorically full of light" and "soil" is "plant-earth"). Those CONNECTORS are letters that are used to build compound words.
Exapunks is a programming puzzle game set in a retrofuturistic cyberpunk world with early '90s aesthetic. The tutorial is in a form of an in-world zine. For me it was very immersive.
Portal reloaded adds time portals ontop of the normal portals.
Splitgate is an FPS that adds portals on top of Halo style combat. Very fun but may be hard to find a game these days its kinda dead.
Age of empires 3 is an RTS that adds shipments. These shipments increase the pace of the early game and allow for way more personalized play as well as allowing players to react to different things without shifting their entire build order.
GTFO is a horror fps where you and 3 other human players take on raids and these raids are changed each season. When the raids are retired they are gone. You must beat the lvl 1 raids to unlock lvl 2 and so on.
Radio Commander. Its an RTS where you sit in a tent in Vietnam and give and recieve orders via radio. You have a map that you can mark where things are based on the info you get.
Kenshi has a lot of unique elements. It's sort of like a post-apocalyptic Sims game.
It's very addictive and is one of those kinds of games that surpises you with how much freedom you're given. I've not really seen anything quite like it.
You basically have to restore a wasteland back to lush, green nature.
Much like a city builder, this is achieved by putting down buildings. The twist is that at the end, you can't leave a trace so you need to demolish everything again.
It's not a long game, but I thought it was very satisfying. A relaxing puzzle/city builder with soothing music.
I have a couple kinda unique things to suggest. There is a small indie game called Eversion that you can find on Steam. The core mechanic is about shifting to these different planes of existence to finish levels. You can only shift at certain places and shifting opens up pathways that weren't there before. Its retro style graphics and otherwise very simple controls.
The Turing Test is a puzzle game like Portal, but instead of portals, you have a gun that can be used to move energy orbs from around the rooms to unlock doors. The game feels like it encourages creative problem solving a lot more than most puzzle games.
Catherine. Catherine is a game in a few styles. You spend part of the time at a diner/bar interacting with people. Then you go to sleep and in the dream world you ascend towers using moveable blocks that you must climb. Sometimes you are chased up the tower by a boss enemy. There is no combat in the game. It's about ascending the tower as fast as possible at night and progressing the story by day.
The recently deceased Benjamin Brynn is on his way to the afterlife. The player must interact with Brynn's memories through an eye-tracking webcam to progress, as the game reads and responds to the player's eye movement and blinking - from Wikipedia
It tries to emulate life flashing by your eyes as you are dying. I haven't gotten around to play it but, the concept is cool nonetheless.
Poppy Playtime (2021) : controls the extendable arms separately and solve puzzles that way
Older games:
Psychonauts (2005) : some of the scenes toy around with gravity
Half-life 2 (2004): the gravity-gun was groundbreaking.
Serious Sam (2001) : just a shooter, but the quantity of enemies is so huge that you need to figure out different strategies. It's sort of like geometry wars only in first person view and with gory graphics.
Glover (1998) : it's a 3d platformer, where you control a glove, which needs to get ball through the level.
Head over heels (1987) : control the 2 characters Head or Heels separately or together to solve puzzles.( It was recently released on steam. I haven't tried the remake, but the original can also be found on emulators or online)
Patrick's Parabox: Push blocks around to activate switches and reach the exit but the blocks can be pushed into and out of each other recursively, it's awesome
Fez: Already been suggested so +1 for this, lovely game
Against the Storm
Rogue lite city survival builder with gorgeous art, awesome game mechanics and a fantastic dev team whom have basically built the game in collaboration with the community that’s risen around the game.
The game is definitely not for everyone, but ProsperousUniverse kind of stands alone when it comes to people’s descriptions of niches/genres.
The game is an economy/real-time MMO with no real PvP. “Real-time” not like an RTS but as in “this operation takes many hours or days” and everyone has that same time burden.
It’s a game where planning far outperforms “always online” gameplay, so people end up learning spreadsheet software to optimize everything for themselves.
In addition, the UI is modular like a Bloomberg terminal, so it feels right—you feel like a trader.
The World Ends With You (DS): Asymmetric action RPG where your left hand and right hand are playing different games in parallel, which is deeply connected to the game's themes of individual experience and semiotics. The switch remake unfortunately ditches the core gameplay to make it more widely accessible but the original game is worth getting into.
I am not sure if it qualifies but Paradise Killer is pretty unique all-around. It may seem walking-simulator-ish but the presentation and the overall game-design are definitely a stand out. You're trying to solve a murder mystery and it's completely up to you as the player to decide when you've gathered enough information to make a conviction. There is practically no hand-holding either which is quite rare for a mystery solving/detective game.
I know it might not exactly be what OP asked for but I think the game is worth being recommended more.
Persona - a turn based Pokémon-like RPG fused with a social simulator. Your main way of getting stronger isn't by simply levelling up (although it helps) but by fusing multiple monsters that you catch and spending your limited time available with comrades.
Its retro and really rough around the edges (and QTE heavy) and is more of a life sim than a traditional adventure game, but Shenmue I & II introduced day/night cycles with NPC schedules, has a fun martial arts combat system, and the story is kind of like an 80s martial arts film with a detective kick. There's also gambling, drinking, a little bit of working at the docks, darts, retro arcade games, and some sleuthing to progress the story. Your progress from Shenmue I carries over to II
But again its rough around the edges and sometimes referred to as QTE simulator (or Dock Worker Simulator, as I jokingly call it). But somehow, all these elements blend together well to create a unique game. Not going to be for everyone but I really enjoyed it
Final note: I highly recommend using a controller. I ran into issues with KB+M, especially after remapping keys. It broke some of the QTEs.
Battlezone '98: One of the first notable RTS/FPS hybrids. You drive hovertanks and you build bases and you command other tanks. Set in a secret live war on the Moon, Mars, and Venus between the USSR and the USA during the cold war.
I don't know how many other games have done this (or if anyone actually cares), but Me And My Shadow. It's a 2D puzzle platformer where you have to record your movements to move the shadow version of you in order to reach the end of each level.
It's a discontinued open source game that can be found on SourceForge and has a couple different level packs available for when you complete the ones already included.
Dwarf Fortress mostly doesn't have unique gameplay mechanics or anything; but the Legends viewer certainly is a unique feature, due to how all the systems work together to weave randomly generated stories and history of the world through the entire world generation process. So even though you didn't play the game through all those years, the game still kept track of everything going on while simulating the world creation and you can go through it and see all the battles, conflicts, migrations, rise and fall of civilizations, deaths of monsters, etc.
Opus Magnum. It's an optimization puzzle game. You have to assemble mechanical arms and other bits (that grab, swing, rotate, push, and pull) into contraptions that assemble resources that look like molecular diagrams. Optimization puzzles aren't unique but I felt like the pieces you build the contraptions out of in this game are pretty unique, the game is on a hex grid so rotation can play a big roll. Another interesting thing the game does is that to beat a level you simply have to accomplish a proper assembly, which in itself isn't that hard, but the game grades you on three different metrics (speed, size, cost) and gives you no overall score to tell you how much you should value each metric. In this way it is up to your preferences what you want to optimize for if anything. I had fun trying to minmax every stat separately on every level before building my "compromise" machine was not supposed to make big sacrifices in any field.
A lot of people have mentioned it but I definitely recommend Obra Dinn, haven't played a mystery game as unique and enthralling.
Death Stranding makes the player think about how to walk over difficult terrain with a large amount of cargo on their back without losing their balance and falling down. Most games allow you to run as far and recklessly as you want without having to worry about falling, so it was interesting to actually have to work at it, at least before you unlock various modes of transportation.
Life is Strange - At least the original, the sequels are not quite as unique. It's an interactive story (though still in 3D) where you can rewind time to redo conversations, effectively making "save scumming" a core mechanic. The designers use the fact that you deliberate on your own actions quite well. The story is also pretty unique, but unfortunately there isn't a good way to explain why without spoiling any of it.
Inscryption - On the surface, this seems like your run of the mill card game. But once you get familiar with the mechanics, some other genres start blending with it.
Edit: Should also add:
A Normal Lost Phone - The premise is that you find a phone that someone has lost, and you can use it to slowly uncover the story of the person who lost it and why.
The first two games that came to mind are unfortunately only available on PS4. I'll mention them anyway, just in case they come to PC in future or someone else that has a PS4 is interested: Tearaway Unfolded is a really sweet game in a paper craft world. You manipulate paper scenery to help with platforming and really customise your character in creative ways. Just a unique and charming game. And Gravity Rush 1&2. These games let you alter gravity to fly around a beautiful open world - I've never played something with a traversal and combat system like this.
I agree with Obra Dinn and the Witness as mentioned by others!
This is probably a weird suggestion, but you could emulate Metal Gear Ac!d 2 (PSP game). It's a stealth game (like the rest of the MGS series) mixed with a deck builder, so your actions are dictated by the cards that you play. The second one in particular perfects the formula IMO. It's super satisfying and I'd love to see more games of this type!
Ancient Art of War. Really old RTS where food, morale and exhaustion are all-important. You'd think it'd be a micro-management nightmare but it plays smoothly. Unfortunately not multiplayer and never remade or even imitated, for some reason.