Not really Halloween related...
Recently, in World of Warcraft, they added an NPC called Night Elf Mohawk (actually several of them) stationed near the starting area of the various races. By chatting with this Mohawk, he gives you an item to use at your discretion: the Night Elf Mohawk Grenade. By using said Grenade on fellow players, you give all within range the "Mohawked" buff and also a Night Elf Mohawk head. Lasts about an hour or until the next time you die.