Halo versus is excellent for this purpose. Highly adaptable. Start making up rules with your friends. Some simple examples: a death is one sip, a suicide is three. Picking up a power weapon requires one sip after you pick it up but before you fire it. The victim of an Assassination takes an extra sip. Introduce new gametypes and see what fun rules you think of.
The goal becomes not to win the game (although that frequently results), but to inflict as much drinking as possible on your friends through the game. You're not just trying to kill them, you're trying to make them drink. As a warning, this can be extremely cutthroat, especially if you are the one who always loses to your friends. I just happen to like cutthroat drinking games!