Fathom Productions, Houston

Facing the unknown can be as scary as it is invigorating. The course organizers at Mud Challenger pepper their 3- to 6-mile courses with a devious array of obstacles, many of which remain unknown to racers until they encounter them live in the mud-filled field of play. To this end, the only real guarantee at any given Mud Challenger is that participants will get a little muddy, and get as rowdy as they please at a post-race party complete with food, beer, music, and the chance to make many, many mud angels.