Grimcad/grimreaper?: Spawning themselves in the underground beach area with hotdogs, burgers, and beer, then having a picnic with the Xenos.
Myself: Crashing the server by detonating a 250/250/1000 bomb on Ice Colony, I still stand by my decision.
Rahlzel: Spawning in a bar of Syndicate soap, making it invisible and then using Possess abilities to move it and slip people.
Apop: Spawning in Miniguns for himself with ammo and calling it a test.
Coronel, Myself, Ordukai... Ok basically the ENTIRE admin team: Modding the Ammo Datums and Sound files on guns to do some very stupid shit.
(Thou name will not be given): How the Predators got added to CM.