To access the Password screen, go to the Options menu, highlight "Game Status" and press L+R.

Now enter the following passwords:

BLAST_FIRE      Stronger missiles
DRIVE_ONLY      Disables wheel attachment icons
GO_MONSTER      Big wheels
GO_RAMMING      Increases car's weight and ramming ability
GO_SLOW_MO      Slow motion 
GO_MAX_REZ      Highest resolution - requires RAM expansion pak
HOME_ALONE      Solo play
JACK_IT_UP      Higher suspensions
LONG_MOVIE      See ending FMV 
MIXES_CARS      Can pick the same car in multi-player
MORE_SPEED      Faster cars
NO_GRAVITY      Reduced gravity
QUICK_PLAY      Instant action
RAPID_FIRE      Rapid fire
UNDER_FIRE      Enemies attack simultaneously

Special Moves:

Interceptor Missiles 
Halo Decoy:       Up, Up, Down, Machine Gun 
Afterburner:      Up, Up, Up, Machine Gun 
Missile Swarm:    Up, Up, Right, Machine Gun 

Bull's Eye Rockets 
Road Runner:      Up, Down, Down, Machine Gun 
Stampede:         Up, Down, Up, Machine Gun 
Bastion Rockets:  Up, Down, Right, Machine Gun 

Sky Hammer Mortar 
Turtle Turnover:  Down, Down, Down, Machine Gun 
Crater Maker:     Down, Down, Up, Machine Gun 
Tire Buster:      Down, Down, Right, Machine Gun 

Brusier Cannon 
Cow Puncher:      Down, Up, Down, Machine Gun 
Buckshot:         Down, Up, Up, Machine Gun 
Ricochet:         Down, Up, Right, Machine Gun 

Roadkill Mines 
Bear Hug:         Left, Right, Down, Machine Gun 
Cactus Patch:     Left, Right, Up, Machine Gun 
Hovering Mines:   Left, Right, Right, Machine Gun 

Flamethrower 
Brimstone Burner: Right, Left, Up, Machine Gun 
Oil Slick:        Left, Right, Up, Machine Gun 
Wall of Flame:    Right, Left, Down, Machine Gun 

Note on performing specials:
-You must have desired weapon in arsenal.
-Weapon doesn't have to be the selected weapon.

GameShark Codes

Must Be On            f11695a82400
                      f11695ac2400
 
Unlock All            811912981f1f
Cars/Tracks           8119129a1f1f
                      8119129c1f1f
                      8119129e1f1f
                      811912a01f1f
                      811912a21f1f
                      801912a4003f

 
Invincibility         811815720008

 
Rapid Fire            811815720800

 
Enhanced Missile      811815720400

 
Reduced Gravity       811815720002

 
No Enemies Present    811815720004

 
Can Chose Same Cars   811815720020

 
Hardest Difficulty    811815721000

 
Slow Motion           811815722000

 
Ultra Hi-Res          811815724000

 
Big Tires             811815720001

 
Invincibility         811815720808

& Rapid Fire 
 
Invincibility/Rapid   811815720c08
Fire/Enhanced Missles
 
Super Abilities/      811815720f0f
Health 

Thanks to Revolution readers Marcus Donald, matt, and Andrew!