These following list of codes will only work on the European PAL version of the game.
Unlock ALL Weapons and Infinite Ammo: If you're struggling with the game and feel you need more fire power to be able to reach the next level then press 'Start' and highlight Weapons and press Right + L2 + R2 + Square + Circle + X. You'll now have ALL the weapons in the game and an unlimited amount of ammo.
Unlock Stage Select: If there is a particular stage you want to play then press 'Start' and choose Options. Then highlight 'Select Mission' and press Left + L1 + R1 + Select + Square + X.
Unlock Hard Mode: If you want to play a more difficult version of the game then at the 'New Game' title screen press Left + L1 + R2 + Select + Square + Circle + X. If you have entered the code correctly Gabe will say 'Damn it!' as confirmation.
Unlock ALL Weapons and Unlimited Ammo in Current Level: To enter this code pause gameplay and highlight the 'Weapons' option. Then hold Select + L1 + L2 + R2 + Circle + X.
Unlock Level Select: During gameplay pause the game and select 'Options' and then highlight 'Select Mission'. If you now hold L1 + L2 + R1 + Square + Circle + X a list of ALL the levels in the game will appear.
One Hit kills: During gameplay pause the game and highlight 'Objectives' and then hold Right + L1 + R1 + R2 + Circle + X. If you have entered the code correctly Gabe will say 'Understood' as confirmation.
One-Shot Kill: During gameplay pause the game and highlight 'Silenced 9mm' and press Left + Select + Square + X + L1 + R2.
Unlock Super Ammunition: During gameplay pause the game and highlight the 'Map' menu and press Right + R1 + R2 + X.
Unlock Weak Enemies: During gameplay pause the game and highlight the 'Map' menu and press Right + L1 + R1 + X.
Take out the two guards behind the truck with the Gas Grenades found in the locker inside of the guard's room. Snipe out the guard on the over-head walk way THEN the search light (if you shoot the search light first, the guy will call for back-up, making your life a living he).
Go forward until you see the first gas-tank, but take out the guard tha's coming around the corner from the left, first. Look where the guy just came from and take out the guard patrolling in front of the gate. NOW plant the C-4.
Check to your left and see the guy coming down the ramp. Wait for him to leave, and Check your right. Take out this guard using the peek-a-boo tactic (see him when his back is turned) and head up the ramp.
Cross the walkway and wait atop until the two guards leave the scene. Kill the remaining guard and get the Night-Vision Rifle and Gas Grenades. Throw a Gas Grenade to kill the two guards aroung the corner and then sneak up and wait by their bodies. Kill the two guards on the walk-way next to the light and then take out the light. Walk ahead a few feet and kill the guard through the window, and plant the second C-4.
After the C-4 turn to your right and kill the guard past the boxes, make you way down the alley, gas the talking guards and take out the lights. head to your right and plant the third C-4.
Walk towards the tank but when you see the special guy, run all the way back and hide until he turns around, then kill him and pick up his card, FLAK, and ammo. Walk ahead, kill any remaining guards, and plant the fourth C-4.
Kill the guards around the corner and next to the door and open the gate, Head to the Power plant and kill the patrolling gaurd, HURRY kill the other guard next to the switch before he calls for backup. Hit the switch, and plant the final C-4. Now make your way to the bunker and prepare for a lot of guards in the next level.
Go out the window in the bar into the back alley. Look up to see two fire escapes. Climb onto the dumpster and get onto the fire escape opposite the bar first, then jump up to the pipes and go hand over hand to the other fire escape. Be careful, because two terrorists will run out to shoot half way across the pipe. After taking care of them, drop down onto the fire escape and open the box for the grenade launcher. This makes the grenade thrower in the subway section much easier to handle.
Getting through the subway
Go to the opposite end of the subway after it explodes. Use the flashlight on the left of the tracks to find the C-4. Get the C-4, then go to the right hand side. Look up to see the upper level. Press Triangle to climb onto the red crate. Press Triangle to keep climbing up through the debris until the top is reached. This is the only way to exit the lower level.
Find the card keys to get through the gates in the museum. Check all the guards and people that are killed; they usually carry card keys. For the gate in the Rocket Room, shoot the control panel on the third level that keeps sparking while your character is standing on the elevator to reach to that level. The man with the card key is up there.
The only way to defeat Rhoemer (the final boss) is with Gas grenades, which can be found in the upper right room of the last level.
Go to the options menu and highlight the select mission option. With that highlighted, simultaneously press and hold left, R1, L1, select, square, and X If done correctly a menu with all the levels should appear.
2. All Weapons & Infinite Ammo:
Highlight the wepons menu. With that menu option highlighted, simultaneously press and hold: right, R2, L2, circle, square, and X
3. Hard mode:
At title screen press and hold: left, L1, R2, select, square, circle, and X.
4. Super Ammo
Start the game and hit pause. Then, highlight the map menu and press: right, R1, R2, X If done correctly you will hear a laugh.
5. Weak Enemy Cheat:
Press start and Highlight the "map option" and press and hold(at the same time): Right+L2+R1+X
6. When fighting the helicopter, when it is about to shoot you, dive roll out of the way then right away press R1 and shoot. Keep doing that until he is dead.
This is a cheat for all the weapons availiable on the level with unlimited ammo. Press start during gameplay and highlight the weapons option, the press R2+SELECT+L2+L1+Circle+X. Trust! this cheat works.
ok you know when you start the game go to the bar around the corner and shoot the glass and walk in and go past the pool table and follow the hall way.
When you get to a little room with a guy in it shoot him in the head and climb inand go through the window and turn right and go to the box on the left and climb on it and hit up triangle.
Climb on top of the gate lookin thing and walk to the end and jump up on the pole and push left and climb across and watch out for the guy on the ground and aim on them.
Make them eat lead and keep going across the pole and drop on the other side of the gate lookin thing and in front of you there will be a box open it and get the m-79.
Then go back across and drop down and make sure you turn around and climb down or you'll die and have to do it over and go down and turn left and shoot the lock on the gate with you 9mm and walk in and go to the elevater switch.
Hit triangle and wait for a few seconds or so and get on it and hit trianglewhen it said elevater on the platform and go down and turn on you flashlight and go left to the wall and look for a bunch of controls.
Hit the one thats said somthing and hit triangle and them leon will talk to you and then go back to the elevater and get on it and press triangle and go up and shoot the guy on the ledge.
Go back through the gate and go all the way to the wall and turn left and you have to take over now just follow your map and i hope this code helps.