While in the multiplayer section, highlight a, locked level, and press L1+R1+SQUARE to unlock all the multiplayer maps

Press L1 and hold up down circle squre and left on briefing and you should have all the weapons!!

Pause game play, highlight the 'Weapons' option, then hold Right + L2 + R2 + Circle + Square + X. Note: Only the weapons normally available during the current level will become selectable. Note: Hold Select + L1 + L2 + R2 + Circle + X in the PAL version of the game. Hold L2 + R2 + Square + Circle + X in some CD-R versions of the game.

While playing Mini Game pause the game highlight Map and press Right+L2+R2+Square+X+Circle.Now the End Level will be opened!

Defeat the game to unlock the 'End Level' cheat. This will allow you to end the level in missions and mini-games.

Highlight the 'New Game' option on the title screen, then hold Left + L1 + R2 + Select + Square + Circle + X. The phrase 'Damn it' will be spoken to confirm correct code entry. Note: Hold L1 + L2 + R2 + Square + Circle + X in the PAL version of the game.

To get the game in hard mode:
1.) Let it highlight New Game
2.)Hold up, Select, L1, R2, Square, Circle, and X, and you'll enter the next menu. Highlight one player and repaeat to start the game on Hard Mode.

In the Jungle level, rescue the two women. This will make it available in the multi-player mode.

Pause game play, highlight the 'Select mission' option, then hold Left + R1 + L1 + Select + Square + X. Note: Hold L1 + L2 + R1 + R2 + Square + Circle + X in the PAL version of the game.

Pause game play, highlight the 'Silenced 9mm' selection under the 'Weapons' option, then press Left + L1 + R2 + Select + Square + X. Gabe will say 'Understood' to confirm correct code entry. A single shot anywhere on the body of an enemy with any gun will kill instantly. Repeat the code to disable it. Gabe will say 'Damn It' to confirm correct code entry. Note: Pause game play, highlight the bjectives' option, then press Right + L1 + R1 + R2 + Circle + X in the PAL version of the game.

Go to the title screen, highlight 'New Game' than press UP+Select+L1+R2+Square+Circle+X at the same time. You will hear a tone.
Then highlight 'One Player' and press: UP+Select+L1+R2+Square+Circle+X
at the same time. You will hear a tone again.

Beat the game to unlock super agent mode in your cheats menu on the options screen. this cheat makes all shots made by you one hit kills.

after beating the game 3 times..go to the first level again..right when ur about to snipe that guy hitting that hostage..point ur sniper at his head for about 5 secs without losing the word 'head' on ur snipe scope..a cut scene will soon come into play..after beating the guys who barge into ur room..quickly get a shot off on the guy across the street..another cut scene will come into play..IF in the cut scene..gabe is holding a falcon..u have successfully gotten syphon 4 demo..u can play the 1st level only

Suscessfully beat it once. Once starting a new game, pause it and go to the options menu. Turn 'Super Agent Mode' on to activate one-hit kills.

Locate the area in level 1 where your character jumps through a window to get to the elevator. Go straight and jump over the boxes. There are pictures on the wall that resemble doors. Approach the middle picture where the Flak Jacket is located. Then, game play and enable the 'Weaker opponents' code. The game will resume in a movie theater. Walk into the entrances to the theater (the curtains) to watch the FMV sequences. Press X to advance to the next FMV sequence or press Start to exit. Note: Hold L2 + R2 + Select + Square + X in the PAL version of the game.

Pause game play, highlight the 'Map' option, then press Right + L2 + R1 + X. A laugh will confirm correct code entry. Note: Hold Right + L1 + R1 + R2 + Circle + X in the PAL version of the game.