The sticky frozen sludge that grows six inches of snow, ice, dirt, road salt and debris behind the wheels of your rice burner during the winter months. If you're smart you kick these off in the parking lot before you get home. If you're evil you kick these off on a cold day when your friend is about to drive somewhere, instant speed bump. If you're an idiot you leave them on so they fall off on the highway and people have to dodge them.
After the snow storm there were massive car turds on my VW. I'm saving them for my next case of road rage.