Unlock Biathlon:
To unlock Biathlon you must go to the hotel level and get you're gear in room 413 you're mission is to kill Shi-Hao and his luietenants. After killing Shi-Hao and the fire-fight has begun his lt's. will come running after a while, to obtain the Mini-Game Biathlon you must kill at least 3 of the lt's. with the air taser. To check if you have unlocked Biathlon, press start and then go to the options menu and click on 'cheats' if it has worked it should show if Biathlon is unlocked.
(send by:Andrew)

Military Base Multi-player Stage:
To obtain the Military Base Multi-player stage you must go to the first level(the hotel) and get you're gear from room 413. With the Silenced Sniper Rifle zoomed in you should be able to see Shi-hao beating a man in a purple shirt.(You must not let the man die) Kill Shi-hao and his lt. one of Shi-hao's men will start shooting at the man in purple, kill the man who is shooting at him, if done right after a second the man in purple will get up and run, Gabe will say 'Got it'. To check if you have unlocked the level press start, go down to options and then click on 'cheats' it should have under 'Unlocked Multiplayer stages' Military Base.
(send by:Andrew)

Jungle level in multiplayer:
Save the 2 women in the Jungle level to unlock it in multiplayer.

Super Agent mode
Successfully complete the game to unlock "Super Agent" mode. Pause the game to access the options menu and enable the "Super Agent" option. In this mode, all shots are one-hit kills.

Hard mode
Highlight the "New Game" option at the main menu. Then, hold [Square] + [Circle] + [L1] + [R2] + [Select] + [Up] + [X].

Alternately, highlight the "New Game" option at the main menu. Hold [Square] + [Circle] + [L1] + [R2] + [Select] + [Up] + [X]. Then, highlight the ''One Player'' option and hold and press [Square] + [Circle] + [L1] + [R2] + [Select] + [Up] + [X]. A sound will confirm correct code entry.

Level select
Successfully complete the game under the hard difficulty setting to unlock the "Level Select" option.

End level
Successfully complete the game to unlock the End Level cheat. This allows you to end the level in missions and in mini-games.

Colorado Bridge level in multi-player mode
Play the Pugari Complex and avoid killing Foreman Jones.

Imazlio Park level in multi-player mode
Successfully complete Matila Compound to unlock Imalzio Park. Note: You cannot complete Matila Compound without getting the Satellite Data. Make sure you get it inside the deer head on the wall. If you need help finding it, save the two Matila being asked where the Satellite Data is. After you finish that, the location of the Satellite Data will be on the map.

Jungle level in multi-player mode
Rescue the two women in the Jungle level to unlock it for multi-player mode.

Kabul level in multi-player mode
Play the Kabul level and kill all seven snipers without being seen without collecting the AU300.

Pharcom Warehouses in multi-player mode
Successfully complete the Waterfront level with a time under 2 minutes.

Rhoemer's Computer Center in multi-player mode
Complete the C-5 Galaxy Transport level without killing the co-pilot.

Rhoemer's Fortress in multi-player mode
Complete the St. George Australia level without being detected before saving all the aborigines.

Rhoemers Labs in multi-player mode
Play the Costa Rican Plantation level and find the female slave that is being beaten by a guard. Kill him and she will ask you to save her friend. Do that, and complete the level.

S.S..Lorelei multi-player level
Complete the S.S. Lorelei level without killing the engineer.

Biathlon mini-game
Use the Air Taser to snipe all the enemies in Room 413 during the first mission.

Get a MIL-15
In the first level, of the game, (THE HOTEL), when you are in the Room 413, try to save the guy in the purple suit. Gabe will say (got it) when you save him. Then when your running down the stairs go into the freezer you will run into him and he will give you an MIL-15

C-5 Galaxy Transport: Level completion
As you start, kill the man that runs up to you. Run to the right side of the plane and kill the hiding enemy. Run through the hall and shoot an approaching enemy. Rhomere will run down the steps, but do not follow him. Kill the man on the steps and collect the UAS-12 and flak jacket from the crate. Run up the steps and hit the switch to your left. Run back to the beginning of the level. Take cover, go into sniper vision, and peer around the corner. Use the same tactics as when Chance was fought in Syphon Filter 2. Shoot him out through the cargo door to complete the level.

C-5 Galaxy Transport: Angry pilot
Run up the stairs to the cockpit without killing the man who comes down just after you see Rhoemer. After you talk to the pilot, he will sneak up the stairs and try to kill you.

Convoy: Flak jacket
After fighting all the soldiers in the valley, turn to the left and you will notice a ledge. Climb up it, and in a crate will be a much needed flak jacket.

Hotel Fukushima: MIL15
When you take out Shi-Hao's men in the first level, save the man in purple. Doing so will unlock a secret arena. When your done with those enemies, follow the path until you encounter a man with a shotgun standing next to a food shelf. Turn right and kick the door open. After a quick conversation, the terrorist/gangster will hand over the MIL15.

Hotel Fukushima: Get into Room 413 without a key
You do not have to get the key to Room 413. Instead, go over to the bellhop at the elevator, take it up, go to Room 413 and press [Triangle]. Gabe will kick the door open.

Pugari Gold Mine: M-79
Parachute in and skip ahead through the communiqué. Turn the parachute around 180 degrees. You should be able to see a ledge with a guard on it. Parachute so you can access the ledge and shoot the guard with your 9mm. He was protecting the M-79. You can use it now or save it for later. From here, you can jump back onto the crane structure. Make sure you take the guard out first. He will have spotted you and can shoot you up badly.

Pugari Gold Mine: Crossbow
After getting the explosives, instead of going right into the tunnel turn right. There will be a crate on a ledge. The crossbow is in the crate. After collecting it, continue with the mission. Note: A crossbow can shoot through a Flack Jacket.

Pugari Gold Mine: Gas Grenades
When you parachute and play as Mujari, shoot the terrorist with a head shot from your pistol and shoot the other guard that walks on the cliff. Then, go to the "Jump here" message that and go to the weapons crate to get the Gas Grenades. You will also get the normal grenades. You will need these weapons for enemies wearing flak jackets. If you happen to stun yourself with a Gas Grenade, your character will put his or her hand over his mouth

Pugari Complex: Get hit by truck
Talk to Foreman Joe. When you are done, kill him and look out of the large window. You will see two headlights turn on. A huge dumptruck will appear and hit the building. Alternately, do not kill him and run outside directly in front of the truck. Aim through the window and shoot him in the head. Turn around and the truck will run over you and hit the building. This may require more than one attempt.

Pugari Complex: M79
After killing Foreman Jones, run up the ramp to go on with the next section. To the right, have Gabe jump up and run back towards the office. There is an M79 in a crate.

Senate Building: Grenades
Enter the women's bathroom (the one without the stalls) and go into the last toilet. A "???" will appear. Press [Triangle] to get ten grenades.

Waterfront: MIL15
After destroying a truck, run towards the open area where you will receive an escort from an MI6 operative. To the right of the loading dock is a MIL15.

Whispering Woods: Corpse
Play a mini-game in Whispering Woods. Run up the steps of the building and slide through the trapdoor. Run down the hall to find a man with no skin on his stomach.

Multi-player Slums: Stay alive
Do move from your position. A good spot to hide is upstairs in the passage with the blooper. Hide by the blooper so you can see into the room and as much as possible around the corner toward the passage you came in. Have a G-18 ready with plenty of ammunition. By the massive hole in the ground, run to the other side by the M-16 and shimmy round against the wall. You can just sit on that tiny ledge. Have a blooper ready. Also, on top of where you get the HK5, get in a small alley near the large ramp. Note: Use the shotgun only at close range. If it is close enough, one shot will kill.

Easy kill:
At the very end of the game, when you go to beat Myra Amarov (sp?) on the subway train, make sure you have this gun called Audi 3000. The audi 3000 can shoot through any surface except for bulletproof glass. You'll find this gun in a box before you see Amarov. Anyways, after you get the gun, you'll keep running and bomb open this door. Amarov will be there w/ a hostage. She's hiding behind bulletproof glass so don't bother shooting. However, on the roof of the train, there's a opening. Climb up this opening and you'll be right above Aramov. Aim the audi 3000 and you should see through the roof of the train and be able to aim at Amarov's head. You'll get a nice clean shot. It's the easiest kill you'll get in the whole game.

End Level
Successfully complete the game to unlock the "End Level" cheat. This allows you to end the level in missions and mini-games.