If you play story mode or any different mode you simply have to be near an enemy and choose a side (left side, right side, frontside or backside) and press square. The character will do a stealth kill which is different from each side! The character will only do a stealth kill if the enemy didn't saw you. Note: You can also perform a stealth kill from the air ( from the front and from the back )
Unlock the Demo Level
At the ''Start Screen'' press: Up, Down, Right, Left, X, X, X. You will now be able to play the level that was available on the free Demo disc prior to the game's release.
Unlock Bonus Stage
At the Title Screen press: L1, Up, R1, Down, L2, Right, R2, Left.
Restore Health
Pause game and then press: Up, down, Right, Left, Square, Square, Square.
Increase Items
At the Item Selection Screen hold R2 + L2 while pressing: Square, Square, Square, Up, Left, Down, Right.
Unlock All Missions
At the Mission Selection Screen press: L1, R1, L2, R2, Right, Square, L3, R3.
Unlock all Characters
At the Title Screen press: L1, R2, L2, R1, Right, Left, L3, R3.
Unlock All Layouts
At the Mission Selection Screen press: R3, L3, R2, L2, R1, L1.
Unlock all Items
At the Item Selection screen hold R1 + L1 while pressing: Up, Square, Square, Left, Square, Square, Down, Square, Square, Right, Square, Square.
Show Score
Pause the game, plug a controller into the second controller port, and with that controller press Right, Right, Left, Left. If you entered the code correctly, the score and time will appear at the bottom of the screen.
Increase Score
Pause the game, plug a controller into the second controller port, and with that controller simultaneously press and hold Li and R1, and then press Right, Right, Left, Left. If you entered the code correctly, the game will automatically resume.
All Special Abilities
Pause the game, simultaneously press and hold L1 and L2, and then press Up, Up, Down, Down, and release L1 and L2, and then press square, square, R1, R2. If you entered the code correctly, a menu will appear at the pause screen.
Unlock B-Side Code
At the title screen, simultaneously press and hold L1 and R2, and then press Down, square, Up, square, Right, square, Left, square. If done correctly, you'll hear a sound. Go to the main menu and select Options. At the Options screen, choose Audio, and at the Audio screen, select Language, where you'll now be able to select B-side.
Unlimited Item Capacity
At the item selection screen, press and hold L1 + R1 + R1 + R2 and press Square, Square, Square, Up, Left, Down, Right, Square, Up, Right, Down, Left.