quadfecta
A legendary beirut/beer pong shot that lands on the tops of four cups simultaneously.  Considered the rarest shot in the game, topping even the trifecta, 2-cup knockover-and-sink, and simultaneous 6-cup game-ending double bounce-in.  Counts as 4 cups and has never happened in recorded history of the game, despite being theoretically possible.

So rare for the following reasons:
1) Only possible with smaller-than-average cups.
2) Only possible when cups are arranged in a perfect square formation (not possible in a standard game).
3) The physics of it happening are similar to those of the trifecta, which almost never happens in itself.
Witnessing Dan's game-ending quadfecta in the semifinals of the Theta Delt beirut tournament was a thing of beauty comparable to seeing the face of God Himself smiling down on you from the heavens.