Mine was once when i was little i was sledding(sleying? whatever) So I was sledding down the steepest hill in our town and instead of a sled I had a disc. If you don't know what that is, it's a plastic sircle with no steering,spins so you can't see where you're going, and has insane amounts of speed compared to a sled. So I was going down the hill and the disk did a 180. Now something you should know about this hill was, it's next to a park. So I'm down at like 20mph(sorry to all the Non-Americans out there, I'm guessing that's about 47kph?) so going down the hill and keep in mind I can't steer. halfway down i notice a bench about five feet away from me. So at about 1 foot i duck and the bench just scrapes my chin. looking back on it, if i hadn,t ducked or been a little bigger I'm guessing i could have completely busted my jaw or had serious head injury.