Just after posting the item about eggs I found this from Dave Barry, who introduced me to a toy.
My daughter and her friend each had a little money to spend, and they decided, after much pondering, to go with the novelty splat egg. This is a ball made of soft plastic with a "yolk" in the middle. The idea is that you throw on the floor, where it splats, so for a moment it looks sort of like a broken egg, but then it forms back into a ball. Ha ha! What fun!
Available here, among many other places I'm sure.