Doom LAN party at a friend of a friend's house.
Had to work that day so I showed up with my computer 10 hours after it started -- party still going strong.
12 systems on 2 LANs spread through the living room and dining room.
An hour later, someone loads up a modded deathmatch level with TONS of ammo/weapons to grab.
The mod changed the sound of picking up an item to Homer Simpson saying "Donuts".
"Do, do, don, donu, do, do, donuts, donuts, do, donuts. . . ." Some of the guys were laughing too hard to play.

It was a running joke for
months.
Scott