Enable the "Invincibility" code when in the Face's Of World level for capture the flag. Get the Redeemer from top of either castle. They are found on the left hyper link. Then enable the "Unlimited ammunition" code to get 999 Redeemers. Fall out of space and you will not die. Just press R2 to shoot the controllable rocket, then try to see how many people you can trace and kill -- but get the other team's flag first.
Additional levels
Successfully complete the game under the inhuman difficulty setting to unlock 7 death match and 4 capture the flag levels. No additional two player levels will be unlocked.
All Characters
Press Start to pause the game, then press Left, Left, Circle, Circle, Right, Left, X.
All weapons
Press Start to pause game play, then press Left, Circle, Right, Square, Right, Left.
Big Head Mutator
At the Main Menu press: Left, Right, Left, Right, Left, Right, Circle, Circle, Circle.
Now, enter the multiplayer option. Select how many players then at the level select screen you can highlight the MUTATORS option and hit X. Highlight the big head option and press RIGHT. Now press the X button and enter the game.
Change Camera View
Hold Circle + X + Start while playing the game. The game will pause. Resume the game with the view fixed.
To return to First Person View, hold Triangle + Square + Start while playing the game. The game will pause. Resume the game with the new view.
Firewire multi-player mode
Note: This trick requires a four port Firewire PC hub. Use Firewire cables to connect the iLink port of one to three more PlayStation2 consoles to the hub. Press Start to pause game play in two player multi-player mode and press Left, Circle, Left, Right, Square, Right. Have all players press Start at the waiting screen.
Four Players without MultiTap
All you need is a "USB" keyboard and mouse to add an extra player. This will also allow you to play four player via two keyboards and two controllers. Set the controller configuration such that the keyboards and mouse's are in the third and fourth player positions.
Gatling Gun From Wolfenstein
To get the Gatling Gun from Wolfenstein, simply press and hold SELECT and then press Up, Up, Down, Down, Left, Right, Left, Right, Square, Triangle, Square, Triangle, and START at the Title screen.
God Mode
During the game you can press the START button and enter:
LEFT, RIGHT, CIRCLE, CIRCLE, CIRCLE, RIGHT, LEFT.
Once you hit the last button you'll be taken back to the game, but this time you're invincible.
Heat seeking feature in rocket launcher
Keep your crosshairs on your opponent. Wait until the crosshairs change into a red "X", then fire your missile.
Infinite health
Pause the game and press Square, Circle, Left, Right, Circle, Square.
Invincibility
Press Start to pause game play, then press Square, Circle, Left, Right, Circle, Square. Alternately, press Start to pause game play, then press Square(2), Circle(2), Left, Right, Circle(2), Square(2).
Level Select
Save your game and go back to the main menu. Once you are at the resume game screen, highlight your saved game and press Up, Down, Down, Up, Left, Up, Right, Down.
Level skip
Press Start to pause game play, then press Up, Down, Left, Right(2), Left, Circle.
Maximum ammunition
Pause the game and press Left, Right, Circle(3), Right, Left.
Quad damage in Tempest
Get the Anti-Gravity Boots and go to the area where the Shock Rifle is located. Up on the rafters is a Quad Damage Power-up.
Rapid fire freehand
Enable the "Full ammunition" code after getting the weapon you want. Resume the game and press the fire button. As soon as you fire, press Start. After you resume the game again, the weapon should fire on its own as many times as desired, until you run out of ammunition. Press R1 again and sometimes it will switch to the secondary weapon. However, you cannot switch back to the first fired weapon. Note: This causes the game to slow down with a rocket launcher or Redeemer.
Skip to Next Level
Pause the game and press Up, Down, Left, Right, Right, Left, Circle.
Stealth Mutator
At the title screen, press Square(2), Circle(2), Square(2), Circle(2). Select multi-player mode and choose the Stealth Mutator.
Target practice
Go into a wide open level that has the Shock Rifle (Facing Worlds recommended). Go to the top of one of the towers, take out the Shock Rifle, and move the Right Analog-stick randomly and fire in secondary fire mode. Then, aim and fire in primary fire mode. If you hit, you will see a small explosion of blue light.
Unlock Fatboy
Go to the title screen and press Circle, Circle, Circle, Up, Down, Down, Up, Circle, Circle, Circle. Now go to the Multiplayer Mode and look for a new Mutator called Fatboy. Turn this on and your character will become fatter for every kill you make and skinnier for every time you get killed.