Cheat menu
 
 At the main menu, press Left(2), L(2), Right(2), Left(2) in the NTSC
 version of the game. For the PAL version of the game, press Left,
 Down, L(2), Up, Right, Left, Up.
 
 All items
 
 Enable the "Cheat menu" code. Then at the main menu, press R, C-Right
 , Right, L, C-Left , Left, C-Right, Right in the NTSC version of the
 game. For the PAL version of the game, press R, C-Right, Down, L,
 C-Up, Left, C-Right, Left. 
 
 Invincibility
 
 Enable the "Cheat menu" code. Then at the main menu, press R(7), Left
 in the NTSC version of the game. If you entered the code correctly,
 you will hear a sound. Now an option for invincibility will appear on
 the cheat menu. For the PAL version of the game, press R, C-Right, R,
 L, R(3), Left. 
 
 Level select
 
 Enable the "Cheat menu" code. Then, press L(3), C-Right, Right,
 Left(2), C-Left in the NTSC version of the game. For the PAL version
 of the game, press R, L, R, C-Down, Right, Up, Left, C-Up.
 
 No monsters
 
 Enable the "Cheat menu" code. Then, press L, C-Left, Left, R,
 C-Right, Right, Left(2), Right in the NTSC version of the game. If
 you entered the code correctly, you will hear the sound of a siren.
 Now an option to toggle monsters on/off will appear on the cheat
 menu. For the PAL version of the game, press L, C-Up, Left, L,
 C-Down, R, L, R. 
 
 Infinite jet pack fuel
 
 While flying with the jet pack, enable the "All items" code.
 
 Big Duke
 
 Start a game in co-op or deathmatch mode. Enable the "All items" code
 and the "Friendly Fire" option. Now have one player shoot the other
 player with the expander gun. Enable the "Invincibility" code before
 the first player explodes, then disable "Invincibility".
 
 Small Duke
 
 Start a game in co-op or deathmatch mode. Enable the "All items" code
 and the "Friendly Fire" option. Now have one player shoot the other
 player with the shrinker gun. Enable the "Invincibility" code, then
 disable "Invincibility". 
 
 Refill health
 
 Destroy a fire hydrant, or another water source. Then, stand in the
 water and hold A to slowly restore health. Alternatively, stand in
 front of a toilet or urinal and press A.
 
  Game Shark Codez:
 
               
  Infinite Health Level 1          
  80247463 00FF
               
  Infinite Ammo (Pistol)           
  802A5A01 00FF
               
  Have All Keys                    
  802A5A47 000F
               
  Have Shotgun                     
  802A5ABB 0001
               
  Infinite Ammo (Shotgun)          
  802A5A03 00FF
               
  Have Sub Machine Guns            
  802A5ABC 0001
               
  Infinite Ammo (SMG's)            
  802A5A05 00FF
               
  Have Grenade Launcher            
  802A5ABD 0001
               
  Infinite Ammo (Grenade Launcher) 
  802A5A07 00FF
               
  Have Pipe Bombs                  
  802A5ABE 0001
               
  Infinite Ammo (Pipe Bombs)       
  802A5A09 00FF
               
  Have Shrinker                    
  802A5ABF 0001
               
  Infinite Ammo (Shrinker)         
  802A5A0B 00FF
               
  Have Expander                    
  802A5AC0 0001
               
  Infinite AMmo (Expander)         
  802A5A0D 00FF
               
  Have Missile Launcher            
  802A5AC1 0001
               
  Infinite Ammo (Missile Launcher) 
  802A5A0F 00FF
               
  Have Plasma Cannon               
  802A5AC2 0001
               
  Infinite Ammo (Plasma Cannon)    
  802A5A11 00FF
               
  Have Laser Trip Bomb             
  802A5AC3 0001
               
  Infinite Ammo (Laser Trip Bomb)  
  802A5A13 00FF
               
  Infinite Armor                   
  812A5A92 0064
               
  Infinite Vitamin K               
  812A5A90 0190
               
  Infinite Jet Pack                
  812A5A8E 0640
               
  Infinite Scuba Gear              
  812A5A8C 1900
               
  Weapon Equipped Modifier         
  802A5A23 000?
               
  Open Cheat Menu                  
  801012D8 0001
               
  Open Invincibility Cheat         
  801012DC 0001
               
  Open Monsters Cheat              
  801012E0 0001
               
  Open All Items Cheat             
  801012E4 0001
               
  Open Goto Level ?? Cheat         
  801012E8 0001