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 :]
Chess. I’ve been playing since I was a kid, and sometimes I’ll create new accounts on chess websites to see how quickly I’ll get them rated to 2000+. I’m living proof that chess players aren’t that smart though because I’m a dumbass when it comes to literally anything else.
Realising you're dumb makes you smarter than 80% of humanity 😎