Invincibility
At the Load screen, press Down, Down, Down, Down, Left, Left, Left, Left, L, R, R, L, C-Up, C-Down. If done correctly, you will return to the Main Menu.

Unlimited Ammo
At the Load screen, press Up, Up, Up, Up, Right, Right, Right, Right, L, R, L, R, C-Right, C-Left. If done correctly, you will return to the Main Menu.

All Weapons
At the Load screen, press C-Up, C-Up, C-Up, C-Up, C-Down, C-Down, C-Down, C-Down, C-Down, C-Down, C-Down, L, R, R + L, R + L. If done correctly, you will return to the Main Menu.

Randomizer Mode
Beat the game under both scenarios. Now when you start a new game, you can choose 'Randomizer mode', which randomly places items in the next game.
Submitted by Mark LaCombe (morning_star20@hotmail.com)

Change Your Clothes
First beat both scenarios for either character in under three hours. You'll see a uniformed zombie to confirm after both missions are completed. Now load your last saved game. From the beginning until you reach the gate to the courtyard of the police department, do not pick up one single item. This will generate a new zombie under the lower stairs around the police department. This new zombie is actually Brad Vickers from Resident Evil 1 (the chopper pilot). After you kill him, push the action button to grab the special key. Now go into the police department and go into the west wing save (the darkroom) and you will see two lockers. Use the key, and you will have new outfits!

Rocket Launcher
Beat either character's first scenario without saving the game in under 2 hours 30 minutes with an A or B ranking to get the rocket launcher with unlimited ammo. It will appear in the next game after the first chest is opened.

Gatling Gun
Beat either character's second scenario without saving the game in under 2 hours 30 minutes with an A or B ranking to get the gatling gun with unlimited ammo. It will appear in the next game after the first chest is opened.

Machine Gun
Beat either character's second scenario without saving the game in under 3 hours with a A or B ranking to get the machine gun with unlimited ammo. It will appear in the next game after the first chest is opened.
Submitted by Mark LaCombe (morning_star20@hotmail.com)

Hunk Mission
Beat either character's second scenario in under 2 hours 30 minutes saving less than twelve times. Hunk is an Umbrella mercenary who must fight through some serious zombie hordes. No puzzles, all action - good stuff.
Submitted by Mark LaCombe (morning_star20@hotmail.com)

Tofu Mission
Beat both scenarios for one character in under 3 hours. Now do the same for the other character. Play the game a third time and beat both scenarios for either character in under 3 hours again. You must save less than 12 times during each scenario and you cannot use any of the bonus weapons. Tofu is, well, a big piece of tofu wielding a knife. Very hard!
Submitted by Mark LaCombe (morning_star20@hotmail.com)
Rankings
Note: All grades will be lowered by one if you save more than 12 times or use any of the bonus weapons.
"S" ranking - Beat the game in less than 1 hour 30 minutes without saving or using any First-Aid sprays
"A" ranking - Beat the game in less than 3 hours without using any First-Aid sprays.
"B" ranking - Beat the game in less than 3 hours.
"C" ranking - Beat the game in 5-7 hours.
"D" ranking - Beat the game in over 7 hours