Level select
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press Up,
 Right, Down, Left, Triangle, Circle, X, Square, X, Triangle, Square,
 Circle. 
 
 Level skip
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press X,
 R1, Triangle, R1, Square, Circle, R2(2), X, Square, Triangle, X.
 
 Invincibility
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press
 Square, Down(2), Square, Down(2), Circle. -From: jun_222@hotmail.com
 
 Refill health
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press
 Right(2), Left, Down(2), Up, Triangle, Circle. If you entered the
 code correctly, the extra option "Health" will appear. Select it to
 refill the life bar. 
 
 Refill ammunition
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press Down,
 Right, Circle, Left, Right, Circle. If you entered the code
 correctly, the extra option "Ammo" will appear. Select it to increase
 your ammunition up to a 32,000 round limit. However, the game may
 display problems if 15,000 rounds are exceeded. 
 
 Maximum firepower
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press Down,
 Right, Down, Right, Triangle. If you entered the code correctly, the
 extra option "Power" will appear. Select it to set your gun's
 firepower to maximum. 
 
 Extra lives
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press Left,
 Down, Right, Triangle, Square, X, Circle.
 
 Extra smart bombs
 
 While playing a game, press Start to display the options menu. Then,
 hold L1 + L2 for ten seconds. Keep those buttons held and press R1,
 R2, X, Triangle, Square, Circle, R1, R2, Circle(2), Square.
 
 Play as a walking corpse
 
 Enter the "Health refill" code to enable the "Health" option on the
 options menu. Then, pause the game immediately after dying, and
 before regenerating. Use the "Health" option to refill the life bar.
 Your character can now move around as a splattered corpse, totally
 invulnerable to enemies. However, since your own actions are limited,
 this trick is of limited value. However, it is an interesting thing
 to try on level 6 or during a two player game. 
 
  Game Shark Codez:
 
                  
  Have All Keys              
  80107AC4 000F
                  
  Always Play Level Modifier 
  8004B134 00??
                  
  Player 1 Codes             
                  
  Infinite Lives             
  800CDF42 001E
                  
  Infinite Ammo              
  800CDF3E 03E8
                  
  Infinite Smart Bombs       
  800CDF40 0003
                  
  Max Power-Up               
  800CDF3C 7FFF
                  
  Infinite Health Level 1    
  800CACAC 4000
                  
  Infinite Health Level 2    
  800CC538 4000
                  
  Infinite Health Level 3    
  800C2388 4000
                  
  Infinite Health Level 4    
  800C42C8 4000
                  
  Infinite Health Level 5    
  800C78C0 4000
                  
  Infinite Health Level 6    
  800BAF10 4000
                  
  Infinite Health Level 7    
  800C7F40 4000
                  
  Infinite Health Level 8    
  800CBEE0 4000
                  
  Infinite Health Level 9    
  800CD164 4000
                  
  Infinite Health Level 10   
  800B0924 4000
                  
  Infinite Health Level 11   
  800BFEB8 4000
                  
  Infinite Health Level 12   
  800C6AAC 4000
                  
  Infinite Health Level 13   
  800C5CB0 4000
                  
  Infinite Health Level 14   
  800C24A8 4000
                  
  Infinite Health Level 15   
  800C802C 4000
                  
  Player 2 Codes             
                  
  Infinite Lives             
  D004B138 0002
  800CDFCA 001E
                  
  Infinite Ammo              
  D004B138 0002
  800CDFC6 03E8
                  
  Infinite Smart Bombs       
  D004B138 0002
  800CDFC8 0003
                  
  Max Power-Up               
  D004B138 0002
  800CDFC4 7FFF
                  
  Infinite Health Level 1    
  D004B138 0002
  800CAD2C 4000
                  
  Infinite Health Level 2    
  800CC5B8 4000
                  
  Infinite Health Level 3    
  800C2408 4000
                  
  Infinite Health Level 4    
  800CC348 4000
                  
  Infinite Health Level 5    
  800C7940 4000
                  
  Infinite Health Level 6    
  800BAF90 4000
                  
  Infinite Health Level 7    
  800C7FC0 4000
                  
  Infinite Health Level 8    
  800CBF60 4000
                  
  Infinite Health Level 9    
  800CD1E4 4000
                  
  Infinite Health Level 10   
  800B09A4 4000
                  
  Infinite Health Level 11   
  800BFF38 4000
                  
  Infinite Health Level 12   
  800C6B2C 4000
                  
  Infinite Health Level 13   
  800C5D30 4000
                  
  Infinite Health Level 14   
  800C2528 4000
                  
  Infinite Health Level 15   
  800C80AC 4000