Assist Leeroy Jenkins in recovering his Devout shoulders in Upper Blackrock Spire on Heroic difficulty.
Title Reward: <Name> Jenkins
The original video which has since inspired copycats, game achievements, a title, TCG card, Hearthstone card, etc.
Caution: contains some strong language.
Edit: It seems that this Warlords of Draenor achievement will be replacing Leeeeeeeeeeeeeroy! (debuted with the achievement system in Wrath of the Lich King) as the source of the player title, <Name> Jenkins.
How to get Leeroy Jenkins guide http://www.youtube.com/watch?v=6_sSts4BDbY