Password screen:
Enter the options screen, select "Game Status" then press L1 + R1.

Ending Sequences:
Enter LONG MOVIE as password.

Submission:
DarryTheOutsider@aol.com

Big Wheels:
Enter GO MONSTER as password.

Submission:
DarryTheOutsider@aol.com

Bigger and Heavier Car:
Enter GO RAMMING as password.

Submission:
DarryTheOutsider@aol.com

Raised up Cars:
Enter JACK IT UP as password.

Submission:
DarryTheOutsider@aol.com

Rapid fire mode:
Enter RAPID_FIRE as a password.

Solo play in arcade mode:
Enter HOME_ALONE as a password.

Special attacks:

Interceptor Missiles
Attack 1: Up, Up, Down, Machine Gun
Attack 2: Up, Up, Up, Machine Gun
Attack 3: Up, Up, Right, Machine Gun
Bull's Eye Rockets
Attack 1: Up, Down, Down, Machine Gun
Attack 2: Up, Down, Up, Machine Gun
Attack 3: Up, Down, Right, Machine Gun
Sky Hammer Mortar
Attack 1: Down, Down, Down, Machine Gun
Attack 2: Down, Down, Up, Machine Gun
Attack 3: Down, Down, Right, Machine Gun
Brusier Cannon
Attack 1: Down, Up, Down, Machine Gun
Attack 2: Down, Up, Up, Machine Gun
Attack 3: Down, Up, Right, Machine Gun
Roadkill Mines
Attack 1: Left, Right, Down, Machine Gun
Attack 2: Left, Right, Up, Machine Gun
Attack 3: Right, Left, Right, Machine Gun
Brimstone Burner
Attack 1: Right, Left, Up, Machine Gun
Attack 2: Right, Left, Down, Machine Gun
Attack 3: Right, Left, Right, Machine Gun