99 ammunition
You have to be in the engine room before fighting the B.O.W. (twelfth save point). Intentionally die when fighting B.O.W. and use a continue. Get the handgun bullets and repeat this until you have 99 ammunition. You can also get other bullets in these locations.
Power control room (grenade rounds)
Boiler room (rocket launcher ammo)
First class cabin (gas launcher rounds)
All characters at start
Play through the game until you get all three members (or even two) into your party. Go to a save point and save the game. Then, intentionally die. When prompted to continue or start a new game, select "New Game". When the game starts, you should begin with the two or three people that you died with.
One hit kills
When you get to the point where you get gas rounds for the grenade launcher, go into a battle against a zombie. Use the gas round immediately before the zombie kills you. After this, select "New Game", "Load Game", or "Continue". When the game begins, anytime you fight anything you will automatically kill your opponent in one hit. There is no need to press [Shoot] or do anything else. This effect lasts until the game is turned off.