Complete Story mode as Helena to unlock Spartan-458 from Halo in all modes except for Story mode.

Unlock Tengu: Complete Time Attack mode with all characters, including the bonus characters.

Unlock Biolab Core stage: Successfully complete Story mode.

Unlock Nassau Station stage: Complete Story mode as Helena to unlock a stage similar to the first stage of Halo 2, the hangar area.

Unlock Ein: To unlock Ein in other modes, play through Story mode as Hitomi and defeat him at the end.

Unlock Gen Fu: Play through the game as Eliot and finish his Story mode.

Unlock Helena: Complete Story mode with all sixteen characters to unlock her in all modes.

Unlock Leon: Complete Story mode as Zack to unlock him in all modes except for Story mode.

Cheat: 30 lives
At arcade mode, enter UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, B, A

Wake up, soldier! You have been called in for duty, and this aint no place for slackers.

Extras: Unverified. On the chapter selection screen hold the BACK button and input D-PAD RIGHT, RIGHT, LEFT, LEFT, BLUE, BLUE.

Unlocks all levels
Platform: Xbox 360
On the mission select screen, hold both the left and right bumpers then quickly input on the d-pad left, left, right, right, then Y, Y

British Campaign: Beat the Not One Step Backwards (Russian Campaign Two)

American Campaign: Beat Rommel's Last Stand (British Campaign Three)