Tough Mudder is like that fat-free frozen yogurt that tastes so good you can't believe it's actually good for you: a race that's as physically challenging as it is a rollicking good time. Except when it's not, as when 2011 participants at the original Bear Creek location in Allentown, PA, were surprised with an obstacle requiring them to eat a habanero pepper and then jump into a pool of ice water.

Indigestion and freezing temperatures are consistent with the spirit of Tough Mudder, a 10–12-mile obstacle course series that bills itself as "probably the toughest event on the planet." It started in Allentown in 2010, the brainchild of former British Special Forces officer, Will Dean, and has since added events in cities across the U.S., Canada, Europe, Japan, South Africa, Australia, and New Zealand – recruiting more than a half million participants along the way.

Expect obstacles like the Berlin Walls (a series of 12-foot walls), Funky Monkey (incline monkey bars greased with butter and mud), and Electroshock Therapy (live electrical wires). Fortunately, Tough Mudder is a team event that's more about camaraderie and finishing together than it is about winning, so you'll have support along the way. And a beer waiting for you at the finish line.

More Information: Anyone with $90–200 can sign up. [June 1;]