For those who haven't seen/heard...
Poker player Ashton Griffin bet a friend that he could run 70 miles in 24 hours. He put up $900,000 to his friend's $300,000 and won the $300K as he finished the 70 miles with an hour to spare.
http://espn.go.com/sports/fantasy/blog/_/name/poker/id/6102087/griffin-runs-way-prop-bet-victory