Something you're just good at with minimal effort and/or you learned much more quickly than average.
For me, it's paper snowflakes. My brain just seems to effortlessly figure out what cuts to make to the paper wedge to make it turn out exactly how I want it. Largely useless, but good fun and was a much-needed ego boost when I was a kid :]
I can look at a small open space (trunk, corner of a room, shelves, etc) a and then look at the item I need to fit in that space and say with a decent amount of confidence "yeah that'll fit perfectly" or "that's gonna be slightly too big"
Yea this is me. I'm really good at packing spaces. I've had to repack people's cars to get everything to fit for long trips or moves. It's like I can see how to make the pieces fit together to maximize space.