These aren't so much codes, as secrets.
Solve the and wait through the ending screens until you are rewarded with the Special Key! Save the game now! You will start again at the beginning, but if you go to the wardrobe room (pictured behind the key) and open that mysterious locked closet. You can change into a new outfit! Lookin' sharp!
Solve the game in fewer than three hours but don't rescure anyone. Wait for the ending screens to go by. A rocket will whiz past. Save the game and start over. You get to start with the rocket launcher. It has infinite ammo. Go nuts.
Play as Jill walk into the dining room with Barry and then walk out. Wesker will say investigate any shots fired. Go back in the dining room and Barry will stop you. Then go to the blood spot and Barry will talk as usual. Go by the grandfather clock. The zombie that was eating Kenneth will come after you and Barry will kill it. After Barry gives you the lockpick, go to Kenneth's body. He now has no legs (eaten!) or clips to pick up.
This isn't a very big secret but it's still cool to look at. When you are in the hall, open the front door and a giant rotting doggie will try to bite off your hand. When you search for Wesker in the hall with Jill stay in one spot and wait for Barry to walk in front of the "camera" and you can see his awesome details.
Game Shark CodesInfinite Health:
Turn knife into Rocket Launcher(Unlimited Ammo):
Turn knife into Flamethrower (Unlimited Ammo):
Thanks to Revolution readers Ben Clyde, James Peddle and Setalcott!