You need 2 pitchers of beer, 20 cups, a long table, and ping pong balls. Sound fun yet? Find a large, flat piece of wood or table (6-9 feet long) and set up ten cups on each side just like bowling pins (1 in front, 4 in back) with all the rims touching. Fill the cups evenly (or unevenly) with the pitcher.
Generally, it's partners, with two on each side. One person tosses the ping pong ball, trying to land it in one of the other team's beer cups. If it bounces out, too bad. If it goes in, one member of the "sunk" team drinks all the beer in that cup and removes it from the table. Then play resumes as the team with the ball now tries to bomb the other team. And so on, with teams alternating players each toss, until all cups are empty. At that point the losers finish the other team's remaining beer. Rinse and repeat.
Distraction (hand-waving, trash-talking) is permitted and encouraged. But if you touch the ball above the cups without it having a chance to go in, you have to finish one of your cups. If the ball somehow rebounds back to your side of the table or onto the floor, it's fair game; anyone can scramble for possession. Keep a rinsing cup handy for the balls; you'll need it.