Cheat Mode:

All items- Press Start during game play, then hold L1 + L2 + R1 + R2 and press X, X, Triangle, Triangle. 
Submitted by Raven - The Maddox

Extra arcade mode features  -  Successfully complete the first three levels in story mode on any difficulty setting to unlock the Village, Chemical Plant, and Planet-X levels in arcade mode. Additionally, Dr. Seth Graven, Dr. Katje Nadir, Fingers McKenzie, Ravelle Velvet, Sebastian Photon, and Angel Perez Bots will also be unlocked as playable characters in arcade mode. 

Tattoo on woman from Chemical Plant - Start any type of match in two player mode. Have person play as the woman from the Chemical Plant mission. The other person can be character. Walk up behind the woman and look at her shoulder to see a rose shaped tattoo on her shoulder.

Scifi Autorifle Grenade - Start any normal game and get a Scifi Autorifle. Press R1 to launch a grenade into your target. This attack will cost ten Scifi shells.

Triple rockets rocket launcher - Select any kind of game (story or arcade) and choose either select the rocket launcher as a weapon or find it in arcade mode. Once it is in your possession, press R1. This will fire three or more rockets at one time. Note: This will take three shells from your rocket launcher.

Character differences - Some characters can endure more damage than others. For example, Siamese Cyborg and Insect Mutant. Others are physically stronger. For example, Tuxedo Cyborg and Zombies. Fast characters include Badass Cyborg and Float Alien, who can run very quickly.

1935 Tomb level reward  -  Successfully complete the 1935 Tomb level in story mode on the easy difficulty setting to unlock Cultist as a playable character in arcade mode. 

1970 Chinese level reward  -  Successfully complete the 1970 Chinese level in story mode on the easy difficulty setting to unlock Chinese Chef as a playable character in arcade mode. 

2005 Cyberden level reward  -  Successfully complete the 2005 Cyberden level in story mode on the easy difficulty setting to unlock the 1950 Village, 1985 Chemical Plant, and 2020 Planet X levels in story mode; Dr Seth Graven. Dr Kate Nadir, Fingers McKenzie, Ravelle Velvet, Sebastian Photon, Angel Perez, and Badass Cyborg as playable characters in arcade mode; and Badass Cyborg, Siamese Cyborg, and Female Cyborg as Bots in arcade mode. 

1950 Village level reward  -  Successfully complete the 1950 Village level in story mode on the easy difficulty setting to unlock the 1950 Village level in arcade mode; and "Period Horror" as a Bot Set in arcade mode. 

1985 Chemical Plant level reward  -  Successfully complete the 1985 Chemical Plant level in story mode on the easy difficulty setting to unlock the 1985 Chemical Plant level in arcade mode; "Usual Suspects" as a Bot Set in arcade mode; and Lumberjack, Malehood, and Waiter as Bots in arcade mode. 

2020 Planet X level reward  -  Successfully complete the 2020 Planet X level in story mode on the easy difficulty setting to unlock the 1965 Mansion, 2000 Docks, and 2035 Spaceways levels in story mode; 2020 Planet X level in arcade mode; Peekabo Jones, Mary-Beth Casey, Jacques Misere, Olga Strom, R108, and Gretel as playable characters in arcade mode; "Space Opera" as a Bot Set in arcade mode; and Tuxedo Cyborg, Red Alien, and Green Alien as Bots in arcade mode. 

1965 Mansion level reward  -  Successfully complete the 1965 Mansion level in story mode on the easy difficulty setting to unlock the 1965 Mansion level in arcade mode; "Horror Shocker" as a Bot Set in arcade mode; and Fishwife Mutant, Hick Hyde, Insect Mutant, Overall Mutant, Police Zombie, Girl Zombie, Skull Zombie, and Jacket Zombie as Bots in arcade mode. Note: Set "Auto Aim" to toggle, leave it on, and crouch to get easier head shots to complete this level easier. 

2000 Docks level reward  -  Successfully complete the 2000 Docks level in story mode on the easy difficulty setting to unlock the 2000 Docks level in arcade mode; "Law and Order" as a Bot Set in arcade mode; and Male Soldier, Female Soldier, Gasmask Soldier, Male SWAT, Female SWAT, and Gasmask SWAT as Bots in arcade mode. Note: There are a lot of snipers in high perches by the waterfront, so be alert in this level. 

2035 Spaceways level reward  -  Successfully complete the 2035 Spaceways level in story mode on the easy difficulty setting to unlock the 2035 Spaceways level in arcade mode. 

Challenge mode  -  Successfully complete story mode to unlock challenge mode, which allows you to compete in different challenging situations.

Unlock Cultist (In Arcade Mode) 

• Complete 1935 Tomb in Story Mode on Easy difficulty setting. 

Unlock Chinese Chef (In Arcade Mode) 

• Complete 1970 Chinese in Story Mode on Easy difficulty setting. 

Unlock Badass Cyborg (In Arcade Mode) 

• Complete 2005 Cyberden in Story Mode on Easy difficulty setting. 

Unlock Extra Characters/Levels (In Arcade Mode) 

• Complete the first 3 levels in Story Mode to unlock the following:
  Levels
  Village
  Chemical Plant
  Planet-X Levels
  Characters
  Dr. Seth Graven
  Dr. Katje Nadir
  Fingers McKenzie
  Ravelle Velvet
  Sebastian Photon
  Angel Perez Bots 

Playing tips: 

• Always configure the game to have weapon change at "never", because while you are into the exit shootin your way through endless amounts of splitters, you don't want to have your shotgun removed just because you walk over a pistol 
  
• In some levels there are things that are explosive. Try shooting at everything first. Say someone was behind a wall and you knew they were there, you just couldn't see them. If there is a barrel near the wall, try shooting it. The guy behind the wall might get killed. 
  
• You don't always have to fight all the badguys. In the mansion level you can walk into a room, and the dear heads start shooting at you and we all know how hard thet are to kill. Remember, you don't HAVE to kill them. Likewise with a zombie. You can only kill it by shooting it in the head. Shooting it anywhere else it will only stun it. If you are cornered, stun them all and run like hell. They aren't smart enough to follow you. 
  
• If you stun a zombie when you were aiming for its head, it can still be killed whilst it is recovering/lying on the floor. You don't have to wait for it to get up again. 
   
• 1950 Village story level reward - Successfully complete the 1950 Village level in story mode under the easy difficulty setting to unlock "Period Horror" as a Bot Set in arcade mode. Complete the level under the normal difficulty setting to unlock the Castle level in arcade mode. Complete the level under the hard difficulty setting to unlock Fishwife Mutant as a playable character in arcade mode; if this is done in less than 3 minutes, the Insect Mutant will be unlocked as a playable character in arcade mode. 
• Challenge mode - Successfully complete the game in story mode to unlock challenge mode, which allows you to compete in different challenging situations. Complete all challenges under a number to unlock a new challenge.
• Challenge 1-A Behead the Undead level reward - Complete all challenges to unlock "The Living Dead" as an Bot Set in arcade mode and Challenge 1-B Putrid Punchout.
• Challenge 1-B Putrid Punchout level reward - Complete all challenges to unlock Green Zombie and Brown Zombie as playable characters in arcade mode and Challenge 1-C Dusk of the Dead.
• Challenge 1-C Dusk of the Dead level reward - Complete all challenges to unlock Police Zombie, Skull Zombie, and Jacket Zombie as playable characters in arcade mode and the next challenge.
• Challenge 2-A Flock Around the Dock level reward - Complete all challenges to unlock Duckman Drake as a Bot in arcade mode and Challenge 2-B Pro Am Duck Shoot.
• Challenge 2-B Pro Am Duck Shoot level reward - Complete all challenges to unlock the "All Enemies Are Ducks" cheat and Challenge 2-C Crispy Duck.
• Challenge 2-C Crispy Duck level reward - Complete all challenges to unlock Duckman Drake as a playable character in arcade mode and the next challenge.
• Challenge 3A Tin Man level reward - Complete all challenges to unlock Robofish as Bot in arcade mode and Challenge 3B Lobster Run.
• Challenge 3B Lobster Run level reward - Complete all challenges to unlock the "All Enemies are Robofish" cheat and Challenge 3C Bowl them Over.
• Challenge 3C Bowl Them Over level reward - Complete all challenges to unlock Robofish as a playable character in arcade mode.
• Challenge 4A Shame if Something Got Broken level reward - Complete all challenges to unlock Challenge 4B Don't Wait Around.
• Challenge 4B Don't Wait Around level reward - Complete all challenges to unlock the "Enemy Bricks" cheat and Challenge 4C Brick Flung High.
• Challenge 4C Brick Flung High level reward - Complete all challenges to unlock the brick as a weapon in arcade mode.
• Challenge 5-A First Impressions level reward - Complete all challenges to unlock The Impersonator as Bot in arcade mode and Challenge 5-B Lasting Impressions.
• Challenge 5-B Lasting Impressions level reward - Complete all challenges to unlock the "All enemies Are Impersonators" cheat and Challenge 5-C Who's he Trying to Impress?
• Challenge 5-C Who's he Trying to Impress? level reward - Complete all challenges to unlock The Impersonator as a playable character in arcade mode and the next challenge. 
• Challenge 6-A Barrel Blast level reward - Complete all challenges to unlock Challenge 6-B Bodyguard. 
• Challenge 6-B Bodyguard level reward - Complete all challenges to unlock Gasmask SWAT as playable character in arcade mode and Challenge 6-C Heist.
• Challenge 6-C Heist level reward - Complete all challenges to unlock Veiled SWAT as a Bot and playable character in arcade mode and the next challenge. 
• Challenge 7-A Shop 'til you Drop level reward - Complete all challenges to unlock Ginger as a Bot in arcade mode and Challenge 7-B Sorry, Was That Your Bag?
• Challenge 7-B Sorry, Was That Your Bag? level reward - Complete all challenges to unlock "All Enemies are Gingerbreads" cheat and Challenge 7-C Everyone Must Go! 
• Challenge 7-C Everyone Must Go! level reward - Complete all challenges to unlock Gingerbead as a playable character in arcade mode.
• Challenge 8-A Girls 'n' Boys level reward - Complete all challenges to unlock Fun-Bunny as a Bot in arcade mode and Challenge 8-B Dinner Dates.
• Challenge 8-B Dinner Dates level reward - Complete all challenges to unlock the "All Enemies are Bunnies" cheat and Challenge 8-C Bone Grab.
• Challenge 8-C Bone Grab level reward - Complete all challenges to unlock Farrah Fun-Bunny as a playable character in arcade mode.
• Challenge 9-A I Can't Hear Anyone Screaming level reward - Complete all challenges to unlock TimeSplitters as a Bot Set in arcade mode; TimeSplitter, and TimeSplitter (Same name, different character) as bots in arcade mode.
• Challenge 9-B Flight Delay level reward - Complete all challenges to unlock TimeSplitter as a playable character in arcade mode.
• Challenge 9-C Space Vandals level reward - Complete to unlock TimeSplitter, different than above, as an arcade mode playable character.
• Time Attack rewards - Win the level under the indicated difficulty setting and time to unlock the corresponding reward.
• Tattoo on woman from Chemical Plant - Start any type of match in two player mode. Have person play as the woman from the Chemical Plant mission. The other person can be character. Walk up behind the woman and look at her shoulder to see a rose shaped tattoo on her shoulder. 
  
• Gameshark Codes 
  
  Master Code (Must Be On) ECB78420 1456E79B 
  Invincible 1CADA668 1456E7A6 
  Invisible 1CADA66C 1456E7A6