For all levels:

R1[5] L2[5].
Sent in by: ison

Get Motorcycle: 
Sent in by eyel65@aol.com
L1,R2,R1,R1,L2,L1 
 
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 - R2, R1, L1, L2, R2, R1, L1, L2, Select, Select 
Big Head Duke - R1 R1 R1 R1 R1 R1 R1 R1 R1 UP 
Little Head Duke - R R1 R1 R1 R1 R1 R1 R1 R1 DOWN 
Big Head Enemies - R1 R1 R1 R1 R1 R1 R1 R1 R1 LEFT 
Little Head Enemies - R1 R1 R1 R1 R1 R1 R1 R1 R1 RIGHT 

Level Select:  Pause the game (while playing) and press DOWN 9 times and then press UP and it will say level select. Now quit the game and go to the main menu. You will now have a option that says Time To Kill. Select it and choose the level you want.

Also reported as  -  To level select go to 2 player game pause during play then press up 9 times and then down 1 time and then quit the game go to the start menu and then push left or right to get all the levels (and push X)

Temporary Invincibility  -  After pausing the game press R1, L2, L1, L2, R1, L1, R1, L2, L1, L2. 

Full Invincibility  -  L2, R1, L1, R2, Up, Down, Up, Down, Select(2 times). 

Unlimited Continues  -  After pausing the game press Left, Right, Up, Left, Right, Down, Left, Right, L1, R1. 

Invisibility  -  After pausing the game press L1, R1, L1, R1, L1, R1, L1, R1, L1, R1. 

Unlimited Ammo  -  After pausing the game press Left, Right, Left, Right, Select, Left, Right, Left, Right, Select. 

All weapons  -  After pausing the game press L1, L2, Up, L1, L2, Down, R1, Right, R2, Left. 

Powered-up weapons  -  After pausing the game press R1, R2, L2, L1, R1, R2, L2, L1, Select(2 times). 

Get All Items  -  After pausing the game press R1(5 times), L2(5 times). 

Get All Keys  -  After pausing the game press Up, Right, Up, Left, Down, Up, Right, Left, Right, Down. 

Inflict Extra Damage  -  After pausing the game press L2, R2, L2, R2, L2, R2, L2, R2, L2, R2. 

View Intro Scene  -  After pausing the game press Select, Up(9 times), Select, L1. 

View Victory Scene  -  After pausing the game press Select, Up(9 times), Select, L2. 

View The Credits  -  After pausing the game press Select, Up(9 times), Select, R1. 

Game Complete!
Hold L2 + R2 and press Square, Triangle, Circle(2 times), Start during game play. 

View Rogue Trip FMV Scene  -  Press L1 + L2 + R1 + R2 at the GT Interactive logo during the opening sequence. 

Big head Duke  -  After pausing the game press R1(9 times), Up. 

Small head Duke  -  After pausing the game pressR1(9 times), Down. 

Big head Opponents  -  After pausing the game press R1(9 times), Left. 

Small head Opponents  -  After pausing the game press R1(9 times), Right. Alternatively, pause game play and press R1(3 times), L1(3 times), R2(3 times), Right. 

View Kilt Scene  -  After pausing the game press Select, Up(9 times), Select, R2 

Secret Areas (hint)  -  You may not know this but on two player mode there are secret areas where you can pick up extra items.

In the dungeon stand where the RPG is and face either of the corridors. Run down it and climb up the parallel wall. Duke will jump into a secret area with armor, steroids and double duke in.

In the castle stand in the large red room which contains the armor. Head out of the room and climb up on of the small walls, then tell duke to climb up the skeleton. Inside there is a RPG!

In the coliseum go to the side of one of the large towers at either end and climb up one of the columns. In one of the rooms there is a freezer and in the other there is an RPG!