Duke Nukem: Zero Hour 

All weapons 
When "Press Start" appears at the opening screen:
press Down, A, Up, L, Z, R, C-Up, C-Down, B, C-Left.
If you entered the code correctly, you will hear a sound.

Rifle with infinite ammunition 
When "Press Start" appears at the opening screen:
press C-Up, C-Down, C-Left, C-Right, L, R.
If you entered the code correctly, you will hear a sound.

Freeze Thrower with infinite ammunition 
When "Press Start" appears at the opening screen:
press Down, Up, A, L, R, Z.
If you entered the code correctly, you will hear a sound.

Group 1 multi-player characters 
When "Press Start" appears at the opening screen:
press A, L, R, Left, B, Down, Up. to unlock all Group 1 multi-player characters.
If you entered the code correctly, you will hear a sound.

Group 2 multi-player characters 
When "Press Start" appears at the opening screen:
press B, A(2), R, L. to unlock all Group 2 multi-player characters.
If you entered the code correctly, you will hear a sound.

Group 3 multi-player characters 
When "Press Start" appears at the opening screen:
press L(2), Up, Down, R, B, A. to unlock all Group 3 multi-player characters.
If you entered the code correctly, you will hear a sound.

Group 4 multi-player characters 
When "Press Start" appears at the opening screen:
press B(3), R, Left, A. to unlock all Group 4 multi-player characters.
If you entered the code correctly, you will hear a sound.

Group 5 multi-player characters 
When "Press Start" appears at the opening screen:
press Right, B, Left, L, A, Z. to unlock all Group 5 multi-player characters.
If you entered the code correctly, you will hear a sound.

Group 6 multi-player characters 
When "Press Start" appears at the opening screen:
press Up, Down, B, A(2), Left. to unlock all Group 6 multi-player characters.
If you entered the code correctly, you will hear a sound.

Skin select 
When "Press Start" appears at the opening screen:
press C-Left, R, Left, Up, Down, B, A, Z.
If you entered the code correctly, you will hear a sound.
Skins may be selected in single player mode, but may not be viewed during selection.

First person view 
When "Press Start" appears at the opening screen:
press Down, Up, L, B, Z, Left, C-Up, C-Right, C-Left, Z.
If you entered the code correctly, you will hear a sound.

Action Nuk'em mode 
When "Press Start" appears at the opening screen:
press Down(2), A, Z(2), Left, A. If you entered the code correctly, you will hear a sound.

High speed zombies 
When "Press Start" appears at the opening screen:
press A(2), Z, A, R, C-Down, B. If you entered the code correctly, you will hear a sound.

Big head mode 
When "Press Start" appears at the opening screen:
press B, Up, Down(2), A, Z, A, Right. If you entered the code correctly, you will hear a sound.

Big gun mode 
When "Press Start" appears at the opening screen:
press C-Up, C-Left, Z, B, L, Z, A. If you entered the code correctly, you will hear a sound.

Flat shade map 
When "Press Start" appears at the opening screen:
press Down, Up, Left(2), A, Right, Down. If you entered the code correctly, you will hear a sound. 

Ice skin 
When "Press Start" appears at the opening screen:
press B, Z, Up, L, A, C-Right, A. If you entered the code correctly, you will hear a sound.

Weather 
When "Press Start" appears at the opening screen:
press Z, A, L, B, Down, Up, R. If you entered the code correctly, you will hear a sound.

Debug mode 
When "Press Start" appears at the opening screen:
press C-Up, Up, C-Left, Right, C-Down, Down, C-Right, R, A, B.
If you entered the code correctly, you will hear a sound.
The "Cheats Menu" will be available but will have no cheats active 
(unless they were previously activated or earned).
Once you start or load a game/level, text will appear in the upper/left hand corner of the screen.
Use controller two to control the debug options.
Press Start to cycle through the various lists of options.
Use the buttons noted below to change certain values. 
Note: Debug mode does not save on the memory pak like the other cheats.

  SFX
  L or R: FX down/up 
  Left or Right: FX down/up by 10 
  B: First person view 
  A: Third person view 
  Z: Play SFX 
  Level Warp
  L or R: Level down/up 
  B: Skip level 
  Z: Advance to selected level 
 
  Midi
  L or R: Song down/up 
  A: Play song 
  B: Stop song 
  Global Palette 
  B or A: Red down/up 
  C-Left or C-Down: Green down/up 
  C-Up or C-Right: Blue down/up 

  Cheat
  Z: All weapons 
  L: All items 
  R: All keys 
  A: Invincibility 
  AI Debug Values 
  B or A: GVAR 1 down/up 
  C-Left or C-Down: GVAR 2 down/up 
  C-Up or C-Right: GVAR 3 down/up 

  Fog*
  B or A: Red down/up 
  C-Left or C-Down: Green down/up 
  C-Up or C-Right: Blue down/up 
  Left or Right: NR down/up 
  L or R: FR down/up 

  Sky Top*
  B or A: Red down/up 
  C-Left or C-Down: Green down/up 
  C-Up or C-Right: Blue down/up 

  Sky Bottom*
  B or A: Red down/up 
  C-Left or C-Down: Green down/up 
  C-Up or C-Right: Blue down/up 

  Clouds 1*
  B or A: Red down/up 
  C-Left or C-Down: Green down/up 
  C-Up or C-Right: Blue down/up 
  L or R: HT down/up 
  Down or Up: AN down/up 
  Left or Right: SP down/up 

  Clouds 2*
  B or A: Red down/up 
  C-Left or C-Down: Green down/up 
  C-Up or C-Right: Blue down/up 
  L or R: HT down/up 
  Down or Up: AN down/up 
  Left or Right: SP down/up 

  Player
  L or R: DN Down/Up (changes player's character) 

  GFX
  (Values cannot be changed) 
  AI
  A: AI 0/1 (set to 1 to stop enemies) 
  L: Difficulty 0/1/2 
  R: Auto aim 0/1 

  Alpha Palette
  B or A: R0 down/up 
  C-Left or C-Down: G0 down/up 
  C-Up or C-Right: B0 down/up 
  L or R: R1 down/up 
  Left or Right: G1 down/up 
  Down or Up: B1 down/up 

  Weather Cheat works the same way but only has the options noted with an *