Duke Nukem 64 Codes -

Cheat mode:
Press (x2), (x2), (x2), (x2) at the main menu to access the cheat menu. In the UK version, press , , (x2), , , , . In the French version, press , , (x2), , , , . In the Japanese version, press (x4), (x2), (x2).

Master code:
Press , , , , , , , at the main menu to unlock all options on the cheat menu. Note: If any codes are active, this code will disable them. In the UK version, press , , , , , , , . In the French version, press , , , , (x2), (x2).In the Japanese version, press , , , , , , , .

All items:
Enable the "Cheat mode" code. Press , , , , , , , at the main menu. In the UK version, press , , , , , , , . In the French version, press , , , , , , , . In the Japanese version, press , , , , , , , .

Invincibility:
Enable the "Cheat mode" code. Press (x7), at the main menu. A sound will confirm correct code entry. The invincibility option may now be enabled on the cheat menu. In the UK version, press , , , , (x3), . In the French version, press , (x2), , (x3), . In the Japanese version, press (x7), .

No monsters:
Enable the "Cheat mode" code. Press , , , , , , (x2), at the main menu. The sound of a siren will confirm correct code entry. Monsters may now be toggled on the cheat menu. In the UK version, press , , , , , , , . In the French version, press , , , , , , , . In the Japanese version, press , , , , , , , .

Level select:
Enable the "Cheat mode" code. Press (x3), , , (x2), at the main menu. A level select option will now be available. In the UK version, press , , , , , , , . In the French version, press , (x2), , , , , . In the Japanese version, press , , , , , (x2), .

Unlimited jet pack fuel:
Enable the "All items" code while flying with the jet pack.

Huge Duke:
Start a game in co-op or deathmatch mode. Enable the "All Items" code, as well as the "Friendly Fire" option. Have one player shoot the other player with the expander weapon. Enable the "Invincibility" code before the first player explodes, then disable "Invincibility".

Tiny Duke:
Start a game in co-op or deathmatch mode. Enable the "All Items" code, as well as the "Friendly Fire" option. Have one player shoot the other player with the shrink weapon. Enable the "Invincibility" code, then disable "Invincibility" to get a small version of Duke. Note: Weapons can not be used in this state.

Dark Duke:
Start a game in single player, co-op, or deathmatch mode. Enable all codes except for invincibility. Arm Duke with the plasma rifle or gun. Charge the gun to full power, then shoot it near a wall next to you or shoot the charged blast on the ground. Die, then quickly press and enable "Invincibility". Note: This must be done before the "Press Start" message appears. Resume game play as a darker almost ninja-appearing Duke.

Squished Duke:
Start a game in single player, co-op, or deathmatch mode. Enable all codes except for invincibility. Intentionally get crushed by a door, then quickly press and enable invincibility.

Energy refill:
Destroy any water source, including fountains, fire hydrants, and toilets. Stand in the water and hold to slowly restore energy. Alternately, stand in front of a toilet or urinal and press .