I like Brazilian Jiu-jitsu. I describe it as "play fighting for adults", and it's one of the few sports that has a really wide demographic of players. I can be training alongside professional fighters, lawyers, police, electricians, retail workers, and software engineers - and ultimately anything about you doesn't matter because all you're focusing on is the sport. It's also a great stress reliever, as I can have a terribly stressful day at work, and everything will disappear as I stop a stranger from trying to strangle me.
It's not a particularly popular sport, but it's popular enough that I can pack a gi with me anywhere I go, and find somewhere to train that'll welcome me, and sometimes even let me train for free. While there are some Joe Rogan types that love the sport, my experience has been very good, and have met some of the nicest people from all walks of life.