MOTOCROSS
I grew up racing motocross from the age of 5 to 18. Loretta Lynn's was a place where the national championships were held, not a country singer. I raced ~40 weekends a year, every year.
It's tough to quantify just how much racing shaped who I am today. From a love of travel/adventure (I'd raced in about 15 states before I was 10 years old), to composure under pressure (try lining up against 39 of your fastest competitors from around the country at 8 yrs old), to spatial awareness and leadership (always know where you're at on the track).
I also raced BMX, played hockey, ski/snowboard, and absolutely, postively sucked at baseball.
While I don't ride/race moto now, I'm still an avid fan.