Originally Posted by TheIllusiveMan
You get the awesome Jesters costume. The hat alone gives you a 35% increase to sneaking. You also get Shadowmere.
GameStop tried to convince Bethesda Game Studios, or whomever handles their public realations, to give that hat as a 'GameStop Pre-Order Exclusive'. They, obviously, didn't give any exclusives to GameStop. I ordered the collectors edition anyways.
I forgot about that until you brought up the Jester Costume, it is just an interesting 'factoid'.