Easter Egg: Nightmare...
	Enigma Cheat Codes...
	Mario series reference...
	Quake 3 reference...
	Various Achievements...

Play for about a few hours into the game. Once you arrive at the headquarters of the resistance movement, go to the top floor. There's a mattress on the ground just left of the bulls-eye hanging on the wall. Focusing on the mattress will give you the option to enter a "nightmare." Enter the "nightmare" and you will find yourself in the very first level of Wolfenstein 3D.

Input the listed Enigma Codes to unlock various in game bonus' and modes (located in one of the Tabbed menus by pressing the "Tips and Hints" button)

Effect	Password
999 mode (UBER Difficulty, Health overcharged to 999 but lowers to health 100) and unlimited ammo.	ROW 1 -- (1,2,3,4,5,6,7,8,9) ROW 2 -- (8,7,6,5,4,3,2,1,9)
Hardcore mode (UBER Difficulty, No Health/Armor drops)	ROW 1 -- (3,6,9,3,6,9,3,6,9) ROW 2 -- (6,3,9,6,3,9,6,3,9)
Ironman mode (UBER Difficulty, 1 life/Permadeath)	ROW 1 -- (4,8,3,7,2,6,1,5,9) ROW 2 -- (5,1,6,2,7,3,8,4,8)
Walk in the Park mode (HUD disabled, Death Incarnate difficulty)	ROW 1 -- (2,4,6,8,1,3,5,7,9) ROW 2 -- (7,5,3,1,8,6,4,2,9)

Enter your hideout and go upstairs to Max Haas's bedroom. You should can find Power Stars plushies on his bed.

During the opening sequence for Chapter 6 "London Nautica", Bobby Bram drives Blazkowicz to his objective in London. The keychain hanging from the ignition is a rocket launcher from Quake 3.

Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement	How to unlock
AR magazine + (10 points)	Unlock tactical perk 6.
All that glitters (20 points)	Collect 25 gold items.
Assassin (30 points)	Unlock stealth perk 8.
Autopanzer (10 points)	Unlock assault perk 6.
Bullet feeder (10 points)	Unlock assault perk 4.
Bullseye (10 points)	Unlock demolition perk 4.
Deadeye (10 points)	Unlock tactical perk 1.
Deliverance (30 points)	Release friend.
Double reload (10 points)	Unlock assault perk 1.
Dual-wield expert (30 points)	Unlock assault perk 8.
Endurance I (10 points)	Unlock assault perk 2.
Endurance II (10 points)	Unlock assault perk 5.
Fergus saved (30 points)	Choose to save Fergus.
Grenade pouch + (10 points)	Unlock demolition perk 2.
Grenade pouch ++ (10 points)	Unlock demolition perk 3.
Gun magazine + (10 points)	Unlock tactical perk 4.
Gunner (20 points)	Save allied planes.
Hardened (30 points)	Unlock demolition perk 8.
Heart of gold (30 points)	Collect all gold items.
Hidden in the deep (20 points)	Locate the underwater stash.
Knife sheath + (10 points)	Unlock stealth perk 3.
Knife sheath ++ (10 points)	Unlock stealth perk 4.
Knife throwing (10 points)	Unlock stealth perk 2.
LKW battery + (10 points)	Unlock assault perk 7.
Liberation (100 points)	Complete the game on any difficulty.
London uprising (20 points)	Defeat the London Monitor.
Marksman magazine + (10 points)	Unlock tactical perk 7.
Power to the laser (30 points)	Find the Laserkraftwerk.
Quick draw (10 points)	Unlock tactical perk 2.
Quick regeneration (10 points)	Unlock tactical perk 3.
Quick reload (30 points)	Unlock tactical perk 8.
Rocket magazine + (10 points)	Unlock demolition perk 5.
Scavenger (10 points)	Unlock assault perk 3.
Scout I (10 points)	Unlock stealth perk 1.
Scout II (10 points)	Unlock stealth perk 7.
Secrets revealed I (30 points)	Solve the first Enigma code.
Secrets revealed II (30 points)	Solve the second Enigma code.
Secrets revealed III (30 points)	Solve the third Enigma code.
Secrets revealed IV (30 points)	Solve the fourth Enigma code.
Sentinel (10 points)	Unlock demolition perk 7.
Shotgun magazine + (10 points)	Unlock tactical perk 5.
Silent shot (10 points)	Unlock stealth perk 5.
Super hero (50 points)	Complete game on I AM DEATH INCARNATE! (or ÜBER).
The lives of others (30 points)	Collect all letters.
Throwback (10 points)	Unlock demolition perk 1.
Vampire (10 points)	Unlock stealth perk 6.
Vaporize (10 points)	Unlock demolition perk 6.
Vive la resistance! (20 points)	Locate the resistance.
Wyatt saved (30 points)	Choose to save Wyatt.
Über hero (50 points)	Complete game on ÜBER.