The rules are quite simple; potentially high buzz factor.
Each person starts with a full glass of beer. Any beer will do, but preferably something quite inexpensive.
All players start drinking at the same time. To signal that you have finished you hold the glass upside-down above your head; if anyone does so then the other players must do the same whether or not they have finished drinking.
IMPORTANT NOTE: It isn't required that you actually drink the beer before claiming to have won; the winner is the first person to invert their glass above their head regardless of whether they actually drank the contents.
Note from The Webmixer: IMHO this game is breaks my moral laws. Who in their right mind, drunk or not, would waste a perfectly good beer like this?