Return To Castle Wolfenstein

God mode:
Hold Back and press A, X, Y, B. The phrase "God mode" will appear in the top left corner to confirm correct code entry. Note: This code also works during Wolfenstein 3D.
slaxe and Bruce.

All weapons and full ammunition:
Hold Back and press A, B, Y, X to unlock all weapons and full ammunition for the current level. Note: You must enable this code at the start of each level. When you start running out of ammunition, just enable the code again. Also, this code also works during Wolfenstein 3D.
Bruce.

Wolfenstein 3D:
Successfully complete the game in single player campaign mode to unlock the original Wolfenstein 3D.

Hint Head shots:
Turn off the automatic aim option to get a good head shot. Otherwise, you will lock on to the enemy's body.
commandstation.

Hint: Peeking around corners:
Click and hold the Left Analog-stick while moving it left or right. The only problem is that you cannot shoot.
commandstation.

Hint: Defeating the Super Soldier:
When you first enter the room where you fight the Super Soldier (after the mad doctor talks to you), crouch in the doorway. Press yourself all the way up against the door. If done correctly, the Super Soldier will not see you, and will not leave the room he is supposed to come out of. Use the sniper rifle to shoot him in the head until he dies. Then, jump down and take his Tesla Cannon.
GreatWasabi.

Hint: Multi-player mode: Airstrike:
A lieutenant can call in an airstrike by pressing Zoom, then pulling the trigger on where you want the bombs to drop. There is a ten second delay.
commandstation.

Hint: Multi-player mode: Medical kit:
A medic can help his teammates by switching to the medical kit. Press R to drop it.
commandstation.

Hint: Mission 1: Invincible Kesslar:
In Mission 1: Ominous Rumors, in Part 3: Tram Ride, after Kesslar says "Stop don't shoot! I am Kesslar", do not end the level. Press Back or B and go over to Kesslar. Shoot him as much as desired, but he will not die. You can also go partially into the next level by going through the doors.
Chris Unwin.

Hint: Aliens reference:
The main menu music for the game has been taken directly from James Cameron's film, Aliens. If you own The Deluxe Edition CD of the movie's soundtrack, track 13 (Futile Escape) is the theme for the game's menu.
Elak Swindell.

Hint: 2001: A Space Odyssey reference:
During the last quarter of the game, nearly all the sound effects for the radar equipment, assorted machines, generators, etc. are taken directly from Stanley Kubrick's classic film, 2001: A Space Odyssey. Pod Bay door effects, Pod radar beeps and alerts, and many other easily recognizable sounds are incorporated into the levels.
Elak Swindell.

Key:
H: Dog
P: Pot
S: Soldier
V: Meat
K: Chicken
T: Treasure
A: Ammo
W: Weapon
M: Marine
G: Health
O: Secret room
L: Extra Life
*: Key