The Invisible Bump
More about The Invisible Bump
This is a good dare to do with your friends. What you have to do is walk in front of a few random strangers, then act like something just hit you in the head.
Like pretend you just ran into a long horizontal pipe or something. Then pretend you walk under it so you don't hit your head again. The people behind you will stop and look around trying to figure out what you ran into.
Watch this video to see how it's done. http://www.youtube.com/watch?v=LWz1WRwQKjI