Entry location: Enter these codes in the main menu quickly. You can only have one Challenge Room unlocked at a time, so chose wisely.
Right, Down, Left, Up, Left Bumper, Right Bumper, Y, Y, X, X, Start - Aaron Sedillo's Room
Right Bumper, Y, X, X, Up, Down, Left Bumper, Left Bumper, Up, Down, Start - GamesRadar Challenge Room
Down, Up, Down, Up, Left, LB, X, LB, X, Y, Start - Unlocks Eurogamer Challenge Room
Up, Down, Y, X, X, Y, Down, Up, LB, LB, Start - Unlocks IGN Challenge Room
Left Bumper, X, X, X, Right, Down, Left Bumper, Left, Y, Down, Start - Unlocks the Major Nelson Challenge Room