We used to play Mad-baseball using these when I was younger. It was more of a hybrid of baseball and kickball since you could throw the ball at the runner. We used miniature replica bats that we got at Brewer's games, but I don't remember all the weird rules we came up with.
I do remember that the Madballs were very unpredictable when hit because the surface isn't flat like normal baseballs.
Ahhh, the memories.