... on a similar note of drinks bottle based weapons, find a plastic bottle of between 500ml and 3 litres. Make sure it has a cap that will easilly twist off, Evian mineral water bottles are very good for this. Take the empty bottle and hold it in you hand (or between thighs for a larger bottle), squeeze, aim, and quickly twist of the lid, without really holding it too much. If you get it right, the lid will rifle of at a great speed

With good technique and a good bottle, the lid will go for about 5 meters before slowing down due to air resistance. Generally, when they land, they are still spining quickly.
Its a great trick to play on unsuspecting people. "hey look at this bottle" *pop*