First up, a boat party clip from
Real Girls Gone Bad. Starts with a pretty tame lap dance contest, then switches to a sexual position contest where the constants get completely naked. The losers of the contest are made to do a forfeit. They have to preform oral on each other for a set amount of time.
Second, a male stripper brings a woman on stage and has his way with her in front of the audience. Not a contest of any kind, but fits the theme.
Enjoy,
Slick