Another very simple game (the best kind) with a high buzz factor. Supplies: people, beer, deck of cards, empty bottle.
The deck of cards is placed on the empty bottle. Each player blows cards off the deck on the bottle in turn. The one who blows the last card off the bottle has to drink one glass of beer.
Variation: If somebody spots an ace among the cards a player blew off - that player has to drink once. So if someone blows down a bunch of cards and two aces are visible that person would drink twice.