At the 'Password' screen enter the following codes to unlock the corresponding effect in the game.

Unlock ALL Weapons:
Enter N S R L S

Unlock Max Ammo:
Enter M M L V S R M

Unlock Riff as a Playable Character:
Enter S T P D M N

Unlock Vikki as a Playable Character:
Enter G R N G R L R X

Unlock Hoover as a Playable Character:
Enter S T P D M N

Unlock Plastro as a Playable Character:
Enter P L S T R L V S V G

Unlock Tin Soldier as a Playable Character:
Enter T N S L D R S

Unlock Hail Mendheimicus as a Playable Character:
Enter S H R M N S L D R

Start on Final Level:
Enter D N S T H M N

Unlock Test Info:
Enter T H D T S T

Unlock Debug Display:
Enter T H D T S T

Unlock Small Mode:
Enter D R V L L V S M M

Unlock Large Mode:
Enter L V N G L R G


Unlock Levels

Unlock Level 1 - Spy Blue:
Enter T R G H T R

Unlock Level 2 - Bathroom:
Enter T D B W L

Unlock Level 3 - Riff Mission:
Enter M S T R M N

Unlock Level 4 - Forest:
Enter T L L T R S

Unlock Level 5 - Hoover Mission:
Enter S C R D C T

Unlock Level 6 - Thick Mission:
Enter S T P D M N

Unlock Level 7 - Snow Mission:
Enter B L Z Z R D

Unlock Level 8 - Shrap Mission:
Enter S R F P N K

Unlock Level 9 - Fort Plastro:
Enter G N R L M N

Unlock Level 10 - Scorch Mission:
Enter H T T T R T

Unlock Level 11 - Showdown:
Enter Z B T S R L

Unlock Level 12 - Sandbox:
Enter H T K T T N

Unlock Level 13 - Kitchen:
Enter P T S P N S

Unlock Level 14 - Living Room:
Enter H X M S T R

Unlock Level 15 - Way Home:
Enter V R C L N