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 lived in Canada for 6 months surviving on nothing but being a medical Guinea pig (I had no working permit and due to anonymity, very little was asked of people participating in medical trials, plus they paid a decent amount especially if pain or discomfort was involved); as part of this I went through a raft of IQ tests (there was always some gambling addiction trial going at UofT for some reason) and found out that, like you, I have exceptional visual intelligence - rotating objects in my head, and figuring out if something would fit together was super skills of mine. In every other way I’m decidedly average.