Rulon Gardner, Wrestling, Sydney 2000
Credit: Kim Jae-Hwan / AFP / Getty Images

Russian heavyweight Alexander Karelin was undefeated in 15 years of international grappling, with three gold medals and seven straight world titles. He hadn't allowed anyone to score a point against him in 10 years. Yet, Rulon Gardner, a dairy farmer from Wyoming, showed incredible resolve to pull off a staggering 1-0 win in one of the greatest individual upsets ever.