George Foreman

Sport: Boxing
Career: Two-time World Heavyweight Boxing Champion
Age at Unretirement: 39

Foreman stepped out of the ring in 1977 after having a near-death experience. A decade later he returned to boxing and would regain his world heavyweight title in 1994 by defeating Michael Moorer. In 2004, at the age of 60, Foreman was in the process of planning a second unretirement fight, but nothing ever materialized for this quintessential model for active middle-aged men. Now he spends his time promoting his books and portable cooking grills.