If it was for giggles then skate boarding, would love to be close to 50 and do some awesome tricks but if you mean at a pro level then it would golf.
Baseball. Scrappy little second baseman.
Most of the sexy choices have been taken, can I have High-Stakes Poker?
Golf. Lots of money and a long career, and injuries are rare.
Professional considerations aside (because naturally, I’d like to be good at anything where I could make hundreds of millions of dollars):
Volleyball. To a nerdy midwesterner (me), it always seemed the epitome of California Cool. I took it in PE in college and imagined myself on the A court at Malibu Beach. Unfortunately my 3-inch vertical leap held me back.
It’s pretty obvious.
Sport with best locations.
Sport with coolest fellow-competitors.
Sport with coolest gear.
Sport with most attractive party scene.
Most ‘laid-back’ attitude.
Sport where, when you decide to go on holiday and get away from it all - you just go straight back to where you last competed.
Pro Surfing.
After all these years it’s still baseball. Not for any good reason, but the dream won’t die.
I’m a huge volleyball fan, so that’s where I’d go as well, though I prefer 6-person court volleyball to beach. I’m male, 5’6" and 41 years old, which means that, in the US in particular, I’m the wrong sex, the wrong size, and was around before the libero came into the game.
But I like playing defense, so sure, reset my age and skill and let me play libero at top levels for a while. Plus I don’t have to worry nearly so much about knee problems due to constant jumping.