I dont play World of Warcraft but I have a lot of friends who do, so this is for them. The people in this video spend hours getting their guild members together for some huge raid, then one guy "Leeroy Jenkins" goes off to microwave some chicken during the final spell buffs. When he gets back, he thinks everyone is waiting for him to start the raid, while they are actually putting on the final and most important buffs. He charges in with a battlecry that will forever be known for all of history: "LEEEEEEEEROY JENKIIIIIINS!!!!"
This is such a popular youtube clip (5.5M views +) that there have been several parodies, knock offs, tributes and remixes. Leeroy has made an appearance as a trivia question on the TV game show Jeopardy, and Blizzard is making a Leeroy Jenkins figurine for the WoW Miniature Tabletop Game coming out later in 2008. They might not have succeeded in the raid, but as Leeroy says, "Hey - at least I have chicken."
Leeroy Jenkins Super-Techno Euro-Trance Ultra-Turbo Future-Mix
Leeroy Jenkins on Jeopardy
Leeroy Jenkins 300 Parody
Leeroy Jenkins Halo 3 Parody
Leeroy Jenkins Ninja Loot in World of Offline Gaming
Leeroy Jenkins Wiki