Rack up as many points as you can in the VMU mini-game to unlock the "Eternal Life", "Area Select", "Free Continue", and "Free Time Limit" cheat options in original mode. *Note: Exact number of points is unclear.
Blood Color Option:
Complete the game in arcade mode to open the "Blood Color" option.
Hidden Items in Biological Weapon (Industrial Sewage) Plant Level:
See the fan at the beginning of the Biological Weapon (Industrial Sewage) Plant level? Shoot it (you can not use a button) to collect some hidden items.
Hold Start and press B, X, or Y when choosing your character to have a different outfit.
Select Fighting Mode from the main menu screen and hold start while you select a character. Now, after you choose the Fighting Mode, you will be asked what level you want to start on.
Complete the game in all three original modes to allow free play in arcade mode.
In the begining of the game if you turn left you will see a door. Go through the door and you will see a zombie with flies on it. Kill the zombie and shoot the middle stack of boxes until a box of health falls. This will give you lots of health.
There are two doors in the sewage.One you can get double-pistols and in the other there is a big box of health.
Thanks to Revolution readers Michael Burkett, Tomahawk Sam, Cassie Dodson, Paul and ChronoTrigger!