Bizmo's Brawlpub is the Alliance Brawler's Guild. Found on the Stormwind side of the Deeprun Tram, Bizmo runs the action. A group of battle-hungry fighters has gathered creatures from all over Azeroth and Outland to participate in bloody arena deathmatches with heroes of the Alliance. Above the action is Bizmo's Boom Room, the VIP area for Rank 8 brawlers.
The Horde equivalent is the Brawl'gar Arena.
The full combatant list is on the Brawler's Guild article.