What is your cat's favorite toy?

My fiancee's oldest cat, Max, loves to play with a small ball that he actually plays fetch with. He kicks it to us, he kick it back, he chases it and then carries it in his mouth and kicks it to us. He's simply amazing.

Our other cat, Batman, likes to play with his toy fish and he has a lot of fun chasing it when we throw it. Unfortunately, his other favorite toy is Max, who he consistently bothers.

Oh, and Max loves his pet squirrel (we call it Ryder) and he always has to sleep with it.