Rattleback

A rattleback is a type of toy that looks like a cylinder with a point on one end and flat sides on the other. When you spin it in one direction, it will spin for a while and then quickly spin in the opposite direction. It's like if you played catch with a ball and it came back to you! It's a strange and fun phenomenon that has to do with how the rattleback is shaped and how it interacts with its environment.