Unlimited Ammo
The password "LOADSOFSTUFF:" grants unlimited ammo for any weapon you acquire. The colon at the end is not a typo.

Sound Test
For a sound test, enter the password "JOURNEYS.END"

Level Select
To select any level, enter the password "RABBITBADGER".

Invincibility
For an indestructable car, enter the password "I.AM.IMORTAL".

Final Track
To warp to the endgame, enter the password "ENDGAMELEVEL"