Earlier this year, I was lucky enough to have Can Do Martial Arts set up a Brazilian Jiu-Jitsu class less than 100 meters from my door. Having briefly practiced it in my mid-teens, I jumped at the chance to join.
For those unaware, BJJ is basically body-chess. Your goal is to get your opponent on

Brazilian Body Chess and the French Flight Club
If you are a parkour practitioner and start BJJ, expect to suck even more than the average newbie, but applying groundwork concepts to parkour will completely change your game and lead to cool new possibilities.