Play the secret first person battle mode:
To unlock the first person mode all you have to do is simply complete the game.

Solution to the seven paintings puzzle:
About five hours in on the first disc you'll find a room with seven paintings, each with a switch below it. In order to solve the puzzle you must press the switches below each painting in the correct order. Below is the order in which this must be done.

1. Painting of the Woman
2. Man with two babies
3. Man by himself
4. Man with plate
5. Man with book
6. Man with candle
7. Big painting

Get the rocket launcher:
To obtain the rocket launcher (NOT the linear launcher which is the weapon used at the end of the game) finish the game with a rank S. To acquire an S ranking, you CANNOT save and retry (basically you cannot die or reset the game at anytime) and you CANNOT use health canisters to heal yourself. You must also give the black man at the start of the game the antitoxin and you must save Steve quickly when he takes the golden guns in disc 1. Also you must finish the game within 5 hours.

Linear Launcher:
Get an A ranking with the two Claires, Steve, Chris and Wesker in the Battle Game to unlock the Linear Launcher. Once you gain it, it will automatically appear in your inventory when you begin the Battle Game again

Unlock Albert Wesker:
Complete the Battle Game with Chris Redfield.

Play as alternate Claire in battle mode:
Perform well with the original Claire in battle mode.

Play as alternate Chris in battle mode:
Complete battle mode with Wesker.

Play as Hunk:
Successfully complete the game on the normal difficulty setting in less than three and a half hours and collect all files to unlock Hunk from Resident Evil 2.

Unlock Steve in Battle Game:
Solve a puzzle in the main game. In the underground Save Room in Chris' walkthrough, complete the drawer puzzle in the corner. Grab the Gold Luger to unlock Mr. Burnside.

Defeating Tyrant:
When the Tyrant is limping and leaving large puddles of blood wherever he goes-he bleeds a little after a few hits, but wait until he's bleeding profusely-it's time to hit the blue button and defeat him!

Lock Pick Secret:
When you get the lockpick and go back to the MTF on Disc 1 besides unlocking the glass cabinet in the basement also go up to MTF2 and unlock the cabinet in the room where you put the Skeleton Painting. You will love what you get!

Find D.I.J.'s Journal:
You can find this journal in the Slot Machine in Battle Mode. You may need to play more than once to get it.

Get Albert Wesker:
In the Incubation Lab, take Wesker's sunglasses using Chris.

Infinite Shotgun Rounds:
Enter the room with the 2 paintings of the British Captain and the Facility Model, then go down the ladder and go back up. When you come back up, the shotgun rounds will be behind the pedestal. Go out through the door and return back to the room. Go down the ladder, go back up the ladder and the shotgun rounds will re-appear. Do this as many times as you want.

Shoot the screen:
This is a very obscure cheat I noticed recently. This is sort of like the Re2 cheat where you can shoot the camera. You have to be where you've had Chris and now have Claire again, a little before you meet the Steve-Monster. You go past the first tentacle then get to the second one. Line up so that you only see Claire's back and she is very near to the tentacle (but not within its reach). Take out the grenade launcher, arm the normal rounds and fire at the tentacle. If you do it right the tentacle's green blood should splatter on the camera. Once you move Claire it goes away.

Invisible Exploding Barrel:
When you are playing as Chris in Disc 2, after you solve the oil pressure puzzle and lower the bridge, go into the Airport Office. As soon as you get into the Office, equip the Enhanced Handgun (Modified Glock) and fire one round at the only zombie onscreen. Then without moving at all, fire again. There should be an explosion like you shot an exploding barrel. Finish off the first zombie, and round the desk, and head towards the aquarium. If it is done correctly, the next two zombies will have burning red eyes that leave tracers when they move. It appears that they are also a bit faster and stronger than normal ones

Glitch:
This is just a little glitch I found in the battle game. Get to the part where the 2 hunters attack you at the elevator, after you cap them walk into the elevator and look through the crack and behind the crates. RODRIGO?!