One of the worst: Violet Hold with 4 elitist pricks from my server. Their gear was vastly better than mine, yet their dps was just terrible. Not to mention we wiped on that "astral thief boss" because the tank couldn't be arsed to kite him around. After the wipe they started flaming each other and they all left. WORST GROUP EVAH!
One of the best: It was a late evening and I decided to finish the day with some good old heroics farmin. I got the invite and had the pleasure to run heroics with one of the craziest and funniest group of people I've ever known. They were all Brits, two guys with their girlfriends. They had this hierarchy - the males played a healer (resto shammy) and a clothy (mage) dps while the females played a male DK and a warrior tank. All the comments, all the talk was around how they sucked at their roles, by making sarcastic and funny correlations with things from their everyday life. Oh and did I mentioned they were all drunk and were doing some truly insane things like kiting that boss in UK for "convenience" or taunting the first boss in Nexus "cause she's a NE bitch" and many, many random acts of silliness which made my stomach hurt from laughter. One of the best groups evah.