Various cheats
  
Unlimited Ammo:
     Pause  the  game,  then press R1, Circle, L1, Square, Circle, R1,
Right,  Right, Circle, Right. The game will return to the main menu if
entered correctly. The "Unlimited Ammo" option will now appear.

Unlock All Artwork:
     Pause  the game, then press R1, Square, R1, Square, Circle, Left,
R1,  Left,  Left.  The  game  will  return to the main menu if entered
correctly.  Enter  the  "Extras"  menu  to see an option to unlock all
artwork. 

All Levels
     At  the  level  select  screen  hold  Up on controller two and on
controller one press Start, Select, Select, Square.

All cheats
     Go  to  the  cheat  menu  in  extras menu and enter the following
R2, R1, L1, L2, left, down, right, up, square.


Cheat Mode options
     Beat the game on certain difficulties to unlock these cheats:

Unlockable:              How to Unlock

Big Head Mode            Beat Easy difficulty

Richochet Mode           Beat Easy difficulty

Head Shot Mode           Beat Easy Difficulty

Richochet All Mode       Beat Easy difficulty

Shrink Shot Mode         Beat Normal Difficulty

Dead Eye Mode            Beat Normal Difficulty

Big N' small Mode        Beat Hard Difficulty


'Making of' movies

Unlockable:              How to Unlock

Making of 1              Complete the Russian campaign

Making of 2              Complete the British campaign

Making of 3              Complete the American campaign 
                         (completing the game)