Hi Reddit, what is the most devious or infuriating instance of griefing in an MMO you've experienced or inflicted?

• In WoW, before there were a lot of high levels on the server, maybe three weeks after the beta, my friend took his high level rogue, stalked this horde hunter, and would kill the hunter's pet only. The hunter ended up dual wielding to complete quests. Poor guy.

• A friend of mine played UO where houses which were apparently an expensive thing to get. He would hold open houses under the pretense of selling his house and kill people once they entered the house.

EDIT: Also, I remember that me and a friend infiltrated a fundamentalist christian WoW guild under the pretenses of being reformed Nigerian christians.