The game requires cans of beer and one ping-pong ball.
At the outset, the cans sit at opposite ends of a table, unopened. A player will then throw the ball towards opposing player's unopened can. If the ball hits the can, the thrower may open his can of beer and produceed to drink it as fast as he can. The opposing player must retrieve the ball wherever it goes (under the fridge, behind the TV, into a potted plant, etc.) After retrieving the ball, he must place the ball back onto the table and exclaim "Reeseball!" this is the cue for the thrower/drinker to stop drinking. At this point, the player who retrieved the ball gets to shoot. If the player misses, there is no drinking.
The object of the game is to finish one's beer first. This is most successfully achiveved by hitting the can more times, or getting the ball to richochet wildly so that the opposing player takes longer to retrieve the ball. As with all drinking games, specific rules and regulations are observed by different households, but this is the generic rule of the game.
It may be played head-to-head or by an equal amount of players on two teams.