Easy difficulty bonus
 
 Successfully complete and save the game on the easy difficulty
 setting to unlock a "One Hit Kill" and "Weapons Stay" options for
 multi-player mode. 
 
 Medium difficulty bonus
 
 Successfully complete and save the game on the medium difficulty
 setting to unlock the "Game Speed", "Blast Force", "One Hit Kill" and
 "Weapons Stay" options for multi-player mode.
 
 Hard difficulty bonus
 
 Successfully complete and save the game on the hard difficulty
 setting to unlock the "Unlimited Ammo", "All weapons", "Game Speed",
 "Blast Force", "One Hit Kill" and "Weapons Stay" options for
 multi-player mode. 

 Invincibility 
 To become invincible, pause the game and press L2, L2, R1, R2, R1, L2. 


 
  Game Shark Codez:
 
           
  Reverse Joker Command P1                  
  D00C7DD0 ????
           
  Player 1 Codes                            
           
  Infinite Health                           
  800CBDA0 0064
           
  Have All Weapons                          
  800C7F38 0FFF
           
  Infinite Armor                            
  800C7F1E 0064
           
  Infinite Shotgun & Super Shotgun Ammo     
  800C7F3C 0064
           
  Infinite Machine Gun & Chaingun Ammo      
  800C7F3E 0064
           
  Infinite Grenades & Grenade Launcher Ammo 
  800C7F40 0064
           
  Infinite Rocket Launcher Ammo             
  800C7F42 0064
           
  Infinite Hyper Blaster & BFG Ammo         
  800C7F44 0064
           
  Infinite Rail Gun Ammo                    
  800C7F46 0064
           
  Super Jump (Press Square)                 
  D00C7DD0 8000
  800CBD86 FEC7