Players and NPCs pile in cash and valuable items and then do round-after-round of shots until they either pass out or vomit. Last man (or woman) standing wins the pot.
Each character does an Endurance check, and then adds 10 to the total (dwarfs, and any others with a resistance to poison, add 15). This total represents their capacity to hold their liquor. Each round, when their character downs a shot, the player rolls 1d6 and subtracts this amount from their capacity. (This can be adjusted-- 1d4 for wine, 1d8 for the really heavy stuff, etc.)
When the capacity hits 10 or below, the character is definitely in the bag, and Dazed for the next couple of hours.
When the capacity hits zero or below, the character makes a saving throw against passing out. A successful throw results in 2d12 vomiting. This 2d12 roll really has no effect on gameplay-- it just gauges the amount of vomit, hopefully to the delight and/or disgust of the players. The character is dazed for the next couple of hours, and during this time, they are unable to use healing surges.
If the character fails the saving throw, they pass out. Another player can rouse them to wakefulness by making a DC 25 Heal check; otherwise they remain passed out for a couple hours. If a character is awakened by another, they are dazed, unable to use healing surges, and weakened for the next couple of in-game hours. If a character comes out of it after sleeping, they are merely weakened (save ends).