Hmm, lemme think..
Today at school, we were doing a play. I was being the lobster, and was pretending to be eaten by a shark. So, I dropped down onto my butt, on the cement, and slammed my hand onto the cement as hard as I could. It was pretty painful.
Oh, and I could've sworn I either cracked or moved my jaw in a very weird way, so I couldn't move my jaw for a few seconds :/