Spinning PingPong Ball
This idea is not mine at all but when I saw it last Friday I knew that I had to try it out.
The idea is to make a small tangential hole in a ping-pong ball and put it into liquid nitrogen for a little while. After you remove the ball, the LN2 evaporates and spins the ball.
Obviously heat helps to process so I decided to put the ball in my hands. You get a few small burns when the ball is not spinning, but hey it's fun to have a crazy spinning ping-pong ball in the palm of your hands.