Press R2, L2, Up, Down, Square, Triangle, Circle at the main menu.
Press R2, L2, Up, Down, X, R2, L2, R1, L1 during game play.
Press R2, L2, Up, Down, X, Up, Square, X during game play.
Press R2, L2, Up, Down, X, Up, Down during game play.
Press R2, L2, Up, Down, X, R1, R1 during game play.
Press R2, L2, Up, Down, X, Up, L2 during game play.
Press R2, L2, Up, Down, X, Up, Up during game play.
Press R2, L2, Up, Down, X, L2, L2 during game play.
Press R2, L2, Up, Down, X, Up, L1 during game play.
Press R2, L2, Up, Down, X, R2, R2 during game play. Restart the level to remove its effect.
Press R2, L2, Up, Down, X, L1, L1 during game play. Weapons will pin people to walls when this code is activated.
Hint: Silenced ballers gun:
Successfully complete a level with a "Silenced Assassin" rank.
Successfully complete a level with a "Silenced Assassin" rank twice.
Getting the M4 (M16):
On the motorcade level, you need to clear the town quickly and grab the supplied rifle. Shoot your target. This will cause the UN guards to stop and run on foot to your position. Wait until they get through the gates, then dodge their shots and put them in the cross fire from the remaining troops outside. Since you cannot hurt them, do not shoot. They will soon shoot their own men. Then, just run up and grab an M4. This may not be easy, but it does work.
To get the M4 easier, just use the fiber wire on the UN guards.
Getting the .22SD pistol:
The .22SD is well hidden in the castle level where you have to kill Hayamoto senior. It is one of the items that is displayed in his museum.
Throughout all the levels you will run into many different types of guns. Whenever you see a gun that you do not already have, pick it up. After you complete the level on which you found the gun, the gun will now be available at your house. You will have ammunition in the room for you to use if desired. However, there are many guns that are too big to carry inside your clothes and therefore must be held in the open. You will not be able to pick up a gun of the same size or greater without dropping the one you are holding. You will find other guns on the same level that you cannot pick up because you are already holding one, and the gun you want is simply too big to conceal. In this case, you will have to decide which gun you want more then finish the level with it. You can always replay that level to get the other gun that was left behind.