Cheats

Alternate Costumes
Complete the game once on any difficulty to gain the Special Key to open the costume room where you can change you clothes after completing the game the required amount of times.

Jill's Sarah Connor costume: Complete the game once with Jill on any difficulty.

Jill's Resident Evil 3 costume: Clear the game twice with Jill on any difficulty.

Chris' The Mexican costume: Clear the game once with Chris on any difficulty to unlock his costume where he dresses up like Brad Pitt from the movie The Mexican. Rebecca also changes her costume to look like Julia Roberts from The Mexican.

Chris' CODE Veronica costume: Clear the game twice with Chris on any difficulty.

Invisible Enemy Mode
To unlock this mode beat Real Survival mode once.

New costume for Jill,Difficulty Select and New Title Screen
Complete the game with Jill once and save the game.A few things will change.

1-The main menu will have a different background.
2-If you select the option'Once Again(with your save data loaded)'you will be given a choice of difficulties to begin the next game with-Easy,Normal and Hard
3-You will receive a key that enables you a costume change(in this case Jill's costume)

One Dangerous Zombie Mode
Complete the game as both Chris and Jill one time to unlock the ''One Dangerous Zombie'' option. A special zombie will continue to follow you around during the first part of the game. Shooting this zombie will end the game, so you must avoid it during game play.

Rocket Launcher
To get the Rocket Launcher, beat the game in under 3 hours on Normal or Hard mode.

Samurai Edge
After beating the game on normal difficulty in 5 hours or less with either Chris or Jill, you will have access to the Samurai Edge during the next game.
NOTE: This is NOT a sword.

Unlock Real Survival Mode
To earn Real Survival Mode, complete the game with a single character under 5 hours on normal or hard.

Note: You will also earn Samurai Edge gun.

Glitches

Grenade Launcher Glitch
This is a step by step guide to getting this glitch to work. Follow these instructions or it will fail.

Requirements: You must have the grenade launcher and two types of ammo (e.g., Grenade Rounds, Incendiary Rounds)

1) Put all items in item box
2) Put Grenade Launcher in upper-left item slot
3) Put Incendiary Rounds in upper-right item slot
4) Close box
5) Open inventory
6) Equip Grenade Launcher
7) Open box
8) Select Incendiary Rounds from inventory
9) Press ''A'' twice
10) Move cursor to Incendiary Rounds inside box
11) Press ''A'' twice

The amount of Incendiary Rounds in the Grenade Launcher will now increase. The number value will be graphically glitched. Close the box and open inventory to fix that. I assume the value exceeds the possible amount, so the game automatically reduces the rounds to 240 to prevent data corruption. Enjoy.

This also works for other types of grenade ammo... But why you'd want anything other than Incendiary Rounds is beyond me.

NOTE: This code does not work in the PAL version of the game.

Secrets

Kill Tyrant in one shot
Use Jill and allow Barry to die prior to facing Lisa Trevor. Take his Magnum. Later, while facing the Tyrant, use the magnum. If you hit the Tyrant he will die instantly.

Save time
Open the lid on your gamecube and the time will stop until you put the lid down. This way you can get a better final time.

Resident evil 0 cheats

Unlockables

Unlock New Costumes
If you complete the game on Normal or Hard mode, you'll find the Closet Key in Rebecca's Inventory when you start a new game.

Billy will get a suit and Rebecca will get a leather outfit or a cowgirl uniform.

Easter Eggs
Unlock Leech Hunter Game Beat the game on Easy, Normal, or Hard mode to unlock this mini-game.

Glitches
Save time Open the lid on your gamecube and the time will stop until you put the lid down. This way you can get a better final time.

Secrets

Leech Hunter Rewards
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.

Unlock Ending Bonuses
You can get certain prizes depending on your gameplay rank, which is how fast you beat the game.

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

Unlockables
Alternate Scenario with Claire Beat the game once with Leon on any difficlty and any rank.
Alternate Scenario with Leon Beat the game once with Clair on any difficulty and with any rank.
Extreme Battle Mode Complete both of either character's scenarios with an A rank to unlock it under the ''special'' option on the title screen.
New Costumes To get new costumes in the game,start a new game with either character on Normal. Do not pick anything up. (Anything) When you get to the police station (don't go inside) you will see some stairs. Go down the stairs and there will be a zombie (who is Brad Vickers) Kill him and he'll drop a ''Special Key''. Use the key in the lockers in the dark room and there will be a screen that comes up that asks you if you want to switch costumes. Say yes and you will have the ''new costumes''
Play as Ada Wong (Extreme Battle Mode) Beat Extreme Battle Mode level 1 with any character.
Play as Chris Redfield (Extreme Battle Mode) Beat Extreme Battle Mode level 2 with any character.
Play as Hunk Beat the game with an ''A'' ranking as either character.
Play as Tofu Beat the game using Hunk.
Rocket Launcher Beat the game on Hard Mode and get at least a ''B'' rank. It sould be in your chest when youstart over.

Secrets

How to get all the Ranks
S Rank: Beat the game in 1:30. Use only One herb. don't use any weapon upgrades, no special weapons (like the R. Launcer) and don't pick a weapon up more than one time, like if you pick up the shot gun from the weapon owner, don't go and get it on the police station.

A Rank: Beat the game under 3:00 and don't use any first aid, no special weapons.

B Rank: Just beat the game under 3:00

C Rank: Finish the game in 5 to 7 hours

D Rank: Beat the game over 7 hours

Unlockables

Epilogue Files
When you beat the game for the first 8 times, you would be awarded 8 different Epilogue Files of 8 different Resident Evil Characters, telling you what has happened to each of them after their adventures. Here's the order that you can unlock them in:

Unlockable	How to Unlock
Ada Wong's Epilogue File	Beat the game for the 7th time.
Agent Hunk's Epilogue File	Beat the game for the 8th time.
Barry Burton's Epilogue File	Beat the game for the 3rd time.
Chris Redfield's Epilogue File	Beat the game for the 2nd time.
Claire Redfield's Epilogue File	Beat the game for the 5th time.
Jill Valentine's Epilogue File	Beat the game for the 1st time.
Leon S. Kennedy's Epilogue File	Beat the game for the 4th time.
Sherry Birkin's Epilogue File	Beat the game for the 6th time.

Infinite Bullets

Unlockable	How to Unlock
Infinite Bullets Box	Play from a Next Game save and defeat Nemesis all seven times you meet him.

Jill's Diary

Unlockable	How to Unlock
Jill's Diary	Find and read all files in the game in their particular order. Ex. The file for the 10th folder slot must be the 10th file you read, etc.

Unlock Extra Uniforms

Unlockable	How to Unlock
1 uniforms	Beat the game with a grade of E
2 uniforms	Beat the game with a grade of D
3 uniforms	Beat the game with a grade of C
4 uniforms	Beat the game with a grade of B
5 uniforms	Beat the game with a grade of A

Unlock Mercenary Mode

Unlockable	How to Unlock
Mercenary Mode	To get Mercanary mode (you play as four mercenaries trying to get to the warehouse), simply complete the game on any difficult. In this mode, you can get new features for the real game depending on how well you do.

Secrets

Mercenary Mode Rewards
To unlock the mercenary game, beat the game once on any difficulty.

Every time you play, you will get a ranking and money, the better your performance the better your reward. Completing the mission greatly increases your reward. When you recieve enough money you can purchase a weapons with infinite ammo for the regular game.*

You can purchase the :

Assault Rifle w/ infinite ammo. $2000

Gatling Gun w/infinite ammo. $3000

Rocket Launcher w/ infinite ammo. $5000

Infinite ammo for all weapons. $9999

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Unlockables

Battle Mode
To Unlock The Battle Mode, simply beat the game

Unlockable	How to Unlock
Battle Mode	Beat the Game

Linnear Launcher
How to get the Linear Launcher in battle mode. These times are much harder to achieve than the PS2 versions.

Unlockable	How to Unlock
Linear Launcher	Beat Battle Mode with every character with times under these : Claire 6:00, A. Claire 7:30, Chris 6:30, Steve 10:00, Wesker 30:00,

Unlock Alternate Claire in Battle Game
To unlock Alternate Claire in the Battle Game, beat the Battle Game as the ordinary Claire Redfield.

Unlock Rocket Launcher with Infinite Ammo
To unlock this, beat the game with an A rank

Unlockable	How to Unlock
Rocket Launcher w/ Infinite Ammo	Beat game with A Rank

Unlock Steve Burnside in Battle Mode
Unlock Steve by obtaining the Gold Luger Replica as Chris.

Unlock Wesker in Battle Mode
To unlock Wesker in Battle Mode, beat Battle Mode as Chris.

Unlockable	How to Unlock
Wesker in Battle Mode	Beat Battle Mode as Chris