Being a PvPer, I've occasionally experienced the glitch in Ring of Valor where you fall through the floor of the arena and are immediately portaled back up to near your starting room. I even have one occurence on video, which is fun, with the Skype track paying homage to my immense confusion.
The header image is also a PvP glitch screenshot, believe it or not, from my PvPing priesty friend, the lovely @ameurling. She was doing some 2v2 in Dalaran Sewers and got feared through the wall into what she dubbed the Twilight Zone. This is what Azeroth looks like beyond the conventional world -- a gray space with an expansive, star-speckled sky. And I reckon this is a pretty darn cool glitch. Unfortunately, Alex couldn't get back into Dalaran Sewers -- you win some, you lose some!
So tell me, what glitch have you seen, experienced, heard of, or heard tell of? Is it cool? Is it cooler than Alex's accidental portal from Dalaran Sewers into the Twilight Zone? Tell me all about it.