Warrior Fitness Boot Camp, Brooklyn

With its military-style obstacles and exercises, Warrior Fitness Boot Camp is not for the faint of heart. As Vanity Fair writer Tarik Fayad wrote, "My legs burned ... my arms hung like lead at my sides. ... I was drenched in sweat." But instead of feeling exhausted and discouraged, Fayad was "the happiest I had been in years"—and immediately signed up for three months of unlimited classes.

The boot camp, which was founded by two former Marines, won't mollycoddle participants. Because it doesn't, it gets results and has garnered extensive amounts of press, including appearances on The Dr. Oz Show and CBS's The Early Show.

During its one-hour indoor classes, campers do everything from hoist free weights to run through an obstacle course complete with jungle-gym bars, balance beams, real dirt, and a pool full of sharks carrying switchblades. Kids can also get in on the action—special classes for them help build motor skills and teamwork.