Cloning Items
In any level where you pick up new items and weapons near the beginning, like Chapter 2-1, grab the goods and quit the game. Pick "Continue" immediately and you will still have the items you just picked up. Another copy of the item will still be in its original location. This process can be repeated at will.
Rocket Launcher
The rocket launcher is a powerful weapon that can take out waves of enemies at once and massively damage large foes. Finish the game on any difficulty in less than five hours to get a rocket launcher with infinite ammunition. The cheat is activated in the bonus features section of the main menu.
Character Exclusive Weapons
Upgrade the VZ61 gun to its maximum abilities to unlock the Gatling gun for Chris. Fully upgrade the S75 to get a longbow for his partner Sheva. Get either weapon at the game shop.
Mercenaries Characters
Beating the game once will unlock the "Mercenaries" mode, which means you can return to some places and kill as many enemies as possible within a time limit. Several playable characters can be unlocked in this mode if you earn an "A" grade with 40,000 points when playing alone and 80,000 in a cooperative game. The unlockable characters and their play areas are Tribal Sheva (Missile Area), S.T.A.R.S. Chris (Experimental Facility), Clubbin' Sheva (Ancient Ruins), Jill (Public Assembly), Safari Chris (Village) and evil Wester (Mines).
New Costumes
Chris and Sheva can get new costumes for a second play through. Beat the game on any difficulty to get the "Safari Chris" and "Clubbin' Sheva" outfits. Shoot 25 BSAA emblems to unlock "S.T.A.R.S. Chris" and blast 30 BSAA emblems to play as "Tribal Sheva." These emblems are hidden throughout the game. For example, look for one high on the walls of the warehouse at the start of Chapter 2-1.