BioHazard 0

100 leeches: All weapons found have unlimited ammo.
90-99: Magnum revolver in room 202 of the train.
60-89: Unlimited ammo with the hunting gun.
30-59: Equipped handguns have unlimited ammo.
1-29: Sub-machinegun Bullets added to Rebecca's inventory.

When playing as either Rebecca or Billy and you get bit by a zombie, move the character opposite of your main character directly behind the one you are controlling to have him or her shoot the zombie in the head and kill it in one hit, while the zombie deals you no damage. Note: You must have pistol equipped to save ammunition for a one bullet kill.

When you encounter the first leech zombie (the creatures that are made out of leeches) and have to fight it, you can skip the fight entirely. Simply attempt to walk back down the staircase, and the game will skip to the cut scene that would occur should you stay and fight. It's not much of an advantage in Easy, but in Normal and Hard, this can save you health and ammo.

You can get certain prizes depending on your gameplay rank, which is how fast you beat the game on normal or hard mode.

Here are the ranks and prizes.

D:(9:01 or more) Leech Hunter and Closet Key
C:(7:01 - 9:00) Leech Hunter and Closet Key
B:(5:01 - 7:00) Leech Hunter and Closet Key
A:(3:31 - 5:00) Submachine Gun, Leech Hunter, Closet Key
S:(3:30 or less) Rocket Launcher, Submachine Gun, Leech Hunter, Closet Key

Beat the game on Easy, Normal, or Hard mode to unlock this mini-game.