Capoeira. It's a mix of Brazilian martial arts, music, culture, dance, and game, and one which requires physical training as well as the ability to think quickly and creatively on one's feet, and it teaches you how to truly control your body, something most people never learn to do.

Many people don't know much about it, but it's a beautiful sport. (Martial art, not dance. Common misconception is that it's non-contact - it's only non-contact if you move fast enough!) I particularly enjoy it because of the associated culture and traditions.

(In case anyone's interested, here are some videos: http://www.youtube.com/watch?v=Z8xxgFpK-NM http://www.youtube.com/watch?v=51q1VB_dDik Feel free to email me if you have questions.)