I'm going to assume I can necro this since it's a stickied thread.
My worse would have to be whenever I went into a group with a group was on the first boss of VP (Vortex Pinnacle) right when they came in they were bickering back and fourth
"You can insult me"
"pssh, yah I can"
First words in the dungeon, during the 1st boss about half away in the tank insulted the healer again in mid-fight called her/he a few curse words. The healer stopped healing everyone and caused a wipe. Left the dungeon, not the group. The dungeon.
We couldnt kick her/he, because of the stupid ass kick-system blizzard gots going.
She/he came back like 15 minutes later saying he/she "walked it off" though I was the only one in the group left.
Stupid people.