If they didn't exist today and someone came up with the brilliant idea of having people in control of machines (cars or bikes) moving in opposite directions at 50mph, separated by a few feet and a painted line, it would be dismissed immediately.
Your car. Just think about the forces and mechanisms invovled for this to happen. Every single day we travel at 100km/h in our 2ton at least metal box surrounded by hundreds of other people in their equally large and heavy and fast machines in a space barely wide enough to react in case of an emergency(not even considering if most are actually ready to act in such a case. All of this with realistically little training. Not to mention most people don't really pay attention while driving and certainly don't consider the life of others while doing so. It's so impersonal and dangerous. If it was a never heard of concept, individual cars driven by any normal person would be considered laughably stupid at the very best.
Ladders. Most serious workplace accidents in a lot of trades can be linked back to falling from a hight. Don't be cocky when up a ladder, even little ones.
Capitalism. Most of the other (daily, specific) dangers out there are dangerous because someone's making money off putting other people in danger. I'm including the military industrial complex, but also regular industries and the exploitation of vulnerable populations.
I wouldn't call compressed air extremely dangerous, but more than you'd think.
It can hurt you in a lot of ways and it's often played with like a toy. Like blowing air in somebody's face, don't do that, think of it like coming at them with a handheld drill. Treat an air compressor like any kind of power tool, not exactly dangerous but can hurt you.
Hm, interesting question. Dangerous in which sense?
A kitchen knife can easily kill a person. A match might burn down a house. Everything that produces CO2 or other greenhouse gases is extremely dangerous for the whole world in the long term.