Stolen from wowinsider
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Knight ability Death Grip. If you initiate a duel with a Death Knight who's aboard the ship in Booty Bay while you're standing on the dock, Death Grip will pull you -- not to the ship itself, but all the way across and through the world. Elizabeth Harper has just tried this on live servers ("You get PvP flagged from flying through the arena in Stranglethorn!") and her character finally landed on a random ship in what the map insists is the Alterac Mountains, southeast of where Dalaran used to be.
Death Grip is described as harnessing the unholy energy that surrounds and binds all matter. They certainly got that part right. I don't have a Death Knight online in my guild right now and I'm really curious to see if this just works in Booty Bay, or if it works wherever there's a ship or zeppelin docked. I'm assuming it's the latter; from my admittedly limited understanding of the game's plumbing, once you're on a ship you're not actually where the map "thinks" you are but rather in some nebulous area without real coordinates before the ship transfers you between servers.
UPDATE: A few guildies and I tried this; you'll find additional results and notes behind the cut.