3. Jim Brown
Retirement Age (Career): 29 (1957-1969)
Jim Brown left the NFL as the all-time leading rusher; a record that stood for 19 years. If there's an exact definition of a football player, Jim Brown is it. His running style was so brutal, cats were afraid to tackle him. Shit, he still scares us. Brown left the game to pursue acting (allegedly) and be more involved in political activism. He would later go onto smash Raquel Welch in one of the first interracial sex scenes on film in 100 Rifles. Legend in two games—no Pee Wee Kirkland.