Gymnastics
United States
Age: 25
As the defending Olympic men's champion, Hamm has a lot riding on his return to the rings. His Athens medal was contested by the South Korean runner-up, and not until the Court of Arbitration for Sport declared the gold was his, two months after the Games, could Hamm enjoy his victory. He's back to prove he deserves the title, but it won't be easy. While warming up for the national championships in May, Hamm broke his hand on the parallel bars, requiring surgery and seven weeks to recover.