Several stick out in my mind, but the most annoying that one of my old players wouldn't let die was his mutation of Ashirak. Ashirak was a helpful and major NPC innkeeper of the only inn worth mentioning on the campaign region's frontier. Think of Ashirak as a NG version of Al Sweregen from HBO's Deadwood.....i.e. a local powerbroker.
Anyway, Ashirak, became A** crack for a bunch of players with little experience separating characters from themselves. That was the tip of the iceberg; hardworked campaign world details were forgotten and disregarded at their own peril. They were generally the typical high school gaming group.
I'm in a better group now, but I definetely sympathize with DMs who suffer from disrespect to their lovingly constructed gameworld. Nicknames are good while the in character, but out of character.....they wreak havoc.
Another nickname worth mentioning regards Mogudo Moonshadow, a tiefling rogue/fighter in my last campaign. The player consistently rolled natural 1's about half the time, and generally started to be regarded as the party basket case. The character remained much beloved by the player even after all the players (and myself) jokingly and consistenly referred to him as Mogudo the Failure. He became something of a legend among different gaming groups in our area for his bad luck, and surprisingly he somehow remained the longest lived character in that campaign.
He still games with me, and his current chracter, a halfling monk of St. Cuthbert, has actually remained the only character to survive through the current campaign. His luck has changed for the better.
C.I.D.