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 :]
Reminds me of an obvious/interesting factoid I once saw pointed out:
Every single one of us is at the end of an unbroken line — aaalllll the way back to microorganisms — of folks / critters / etc. that lived long enough to procreate.
Hearty fuckers, every one of us. In a certain sense…