Cheats
From Main Menu, go to Options, Cheat Codes, and then enter these as case sensitive:

BonusBrawl - Unlocks The Dirt Sheet and Mr. McMahon's Office as playable arenas
The Great One - Unlocks The Rock
SuckIT! - Triple H's alternate attire
ViperRKO - Randy Orton's alternate attire
BowDown - Shawn Michaels' alternate attire
Milan Miracle - Unlock Santino Marella'salternate attire
CENATION - Unlock John Cena's alternate attire