http://www.youtube.com/watch?v=igyLU9DjS9Q
I like this one ;D
and this one is kind of kool too :D
http://www.youtube.com/watch?v=xKYoWAon4-I
That first video is a prime example of the now world famous "string theory".
Make any contraption you want and hang it on a string.
Works every time. lol