Kelly Slater
Credit: Steve Robertson / ASP / Getty Images

Why he hung it up: After finishing No. 1 on the Association of Surfing Professionals World Tour six times in the 1990s, Slater didn't have any real challengers.

Why he returned: Andy Irons. The late Hawaii native won three consecutive titles, motivating Slater to return to the sport full time in order to prove his supremacy.

His Success:
 Slater has had a helluva comeback career, with five ASP firsts since 2005.