To be the guild to first kill a boss puts your guild as one of the best out there. The new race in the Burning Crusade has already begun, and can be tracked on many various ways, although us here at SK have decided to bring you some nostalgia as we have compiled a complete list of all the world first kills made in the World of Warcraft history.
To find out who actually killed bosses as Onyxia, Ragnaros, Nefarian, C'Thun and Kel'Thuzad first;
» WoW World First - The Complete List