TBD by Editorial
American Stock/Getty Images

Gene Tunney

1926-28

Known as "The Fighting Marine," Tunney was a thinking man's heavyweight, known for his defense and slick boxing skills. A former light heavyweight champion, Tunney won the heavyweight title by upsetting Jack Dempsey in 1926. He then won the rematch a year later in the famous "Long Count Fight," in which Tunney -- knocked down for the only time in his career -- benefitted from extra recovery time when Dempsey refused to retreat to a neutral corner.

Tunney retired as champion in 1928 at age 31, with his only loss coming against Harry Greb (in the first of their five bouts together) as a light heavyweight.