I used to live with 3 other guys and our rules were...
Fill cups with water, using beer is expensive, ping pong balls get dirty, drinking whats in your hand is convenient.
Drink when the other team scores, obviously.
Shoot from AT LEAST an arms length away. Elbows over the table disqualifies the throw.
2 Re-racks per game, diamond, house, stoplight, etc.
You can scoop the ball out if it's "rimming" and hasn't hit the water yet.
You can swipe at bounces.
2 cups for bounce/trick shots.
If you miss and the ball is still on the table you can attempt to grab it, if you succeed you shoot behind the back.
ON FIRE: If you make 3 shots in a row you throw until you miss. Partners misses do not count against your streak.
Rollback: Both players make it, they shoot again.
Chain Lightning: If a ball hits other cups on its way in those cups are also taken out.
SOLO: Each player can call "solo" on any isolated cup once per game (BEFORE YOU THROW), making the shot ends the game.
Redemption: The losing team has one turn to eliminate all of the victors cups, if they do both teams re-rack with 3 cup pyramids.