Please don't tell me about your "toon." That word drives me to utter distraction. I despair at the idea of players callously shoving their characters out into the boss encounter like so many chess pieces. That's your dude we're talking about! Your avatar, the thing that represents you-ness and all your innovative, adventuresome, heroic purpose! I want to think I'm surrounded by players who are invested in the characters they're playing, rather than simply hopping into them for a quick joyride through LFR before screeching into a parking space and hopping into a new one.
"Toon" doesn't carry the same connotations for plenty of other players, and they couldn't care less about the term. Why should they, when there are so many other pet peeves to fret over -- like players who type "PST whisper" or "PST me." PST is an acronym for "please send tell"; it's not meant, as some players mistakenly believe, to represent the more onomatopoeiaic "psst" sound. There's no need to add anything else after saying PST. In fact, you shouldn't allow your "toon" to "PST anybody," ever. Ouch.
Is there a snippet of MMO lingo that grates on your last nerve? What about it drives you batty?