Brazilian Jiu Jitsu and Muay Thai. BJJ in particular attracts nerds (especially security people, for some reason).
It's because BJJ is a game. You power up by learning new moves, then have to fight against new stronger opponents. Then you have to learn more moves. The game design of other martial arts isn't as deep and complex. Security people like fighting against an opponent, instead of creating something.
There's a few guys I train with, we teach each other tricks. I was beating them until I taught them all my sneaky moves, now I need to learn new moves. Kind of a self-own, but it's forcing me to improve. BJJ makes you get fit but the the tactical and strategic elements are the best part. There are a bunch of engineers, pilots and developers in my gym.