Me and my friends, two of them actually, (makes 3 total) usually play a game of horse, much like the Tony hawk's version found in the games, except with parkour instead of a skateboard. The loser, the one who spelled 'Horse' first, has to do a dare that the others think up for him. Of course it has to be considerable though.
Here are the scores;
Me - 1 loss;
Had to climb on a church and once everyone came out I had to yell "May god be with you"
1st Friend - 2 losses;
Had to pretend to be a "Ball kid" or a "Ball grabber" for a random pair playing tennis.
Had to run through a baseball field while a local game was on. Some junior teams or something.
2nd Friend - 0 loses;
The dares were lots of fun. We've stopped playing though because the 1st friend is a pusillanimous individual, doesn't want to play anymore.