Duke Nukem: Time to Kill Hints/Cheats

Big Heads, Little Heads To change Duke and the enemies's appearance,
pause the game and enter one of these codes: 

Big Head Duke       R1 R1 R1 R1 R1 R1 R1 R1 R1 U 
Tiny Head Duke      R1 R1 R1 R1 R1 R1 R1 R1 R1 D 
Big Head Enemies    R1 R1 R1 R1 R1 R1 R1 R1 R1 L 
Tiny Head Enemies   R1 R1 R1 R1 R1 R1 R1 R1 R1 R 

Note: If you have Big Head Duke and want it to be Tiny Head, then just
enter the Big Head Code again and Duke's head will shrink back to normal
and you can put in the Tiny head code. Otherwise it will not work.
Do the same for Tiny to Big. 
                          
Cheat Codes 
Pause the game and enter these codes at a slow but even pace. 
If you enter them too fast they might not work.

Infinite Ammo -- L R L R SELECT L R L R SELECT 
All Weapons -- L1 L2 U L1 L2 D R1 R R2 L 
All Inventory -- R1 x 5, L2 x 5  
All Keys -- U R U L D U R L R D 
Invisible -- L1 R1 L1 R1 L1 R1 L1 R1 L1 R1 
Double Damage -- L2 R2 L2 R2 L2 R2 L2 R2 L2 R2 
Temporary Invulnerability -- R1 L2 L1 L2 R1 L1 R1 L2 L1 L2 
Super Weapons -- R R L R R L R R L SELECT   

Level Select 
While playing, pause the game and press DOWN 9 times and then press Up
and it should say Level Select. Now quit the game and on the main menu
you will see a new option that says "Time To Kill". Select it and press
RIGHT or LEFT to choose the level you want to go to. Press X to start
playing. 

Beat the Game 
While playing hold L2 + R2 then press Square, Triangle, Circle, Circle,
Start. 
                          

Rogue Trip Video 
Turn on the game. When the GT Interactive logo appears, simultaneously 
press R1+R2+L1+L2.