Some of them are not revealed in the instruction manual, here are the codes to enter. It is a set of directional codes that you enter with the stick or the pad (I prefer the stick)

Afterburner
Use this to give you a boost of speed. You must have Interceptor missiles to use this. It takes 2 missiles everytime you use it. Enter Up,Up,Up, then fire the Machine Gun. (Z at default)

Halo
Use this as a decoy to ward off guided shots, like other Interceptor Missiles. This also takes 2 missiles to use, and you enter Up,Up,Down then fire the machine gun. (Z)

Stampede
This uses Bullseye rockets, this move fires 5 of them in quick succession, Enter Up, Down, Up, then fire the machine gun

Roadrunner
This uses 2 Bullseye rockets, and if you hit a car with it, it will attach itself to it and cause the car to lose control, if not, it will hit a structure or object and can destroy them too. Enter Up,Down,Down, Fire Machine Gun.

Cow Puncher
Uses 2 Bruiser Cannon shots, can send a car flying if it connects, enter Down,Up,Down, Fire machine gun

Buckshot
Belches 6 Bruiser Cannon shots at once, great at close range, enter Down,Up,Up, Fire Machine Gun

Turtle Turnover
Uses 2 Skyhammer Mortar shots, sends a green projectile that can turn a car completely upside down, good on stalled or still targets, bad on moving ones, enter
Down,Down,Down, Fire Machine gun

Crater Maker
Uses 2-5 Sky hammer shots, 5 if you have 5 or more, and 4 or less if you have less than 5, enter Down,Down,Up, Fire Machine Gun Can make a huge crater when it impacts. The crater will fill back up slowly.

Gravitational Mine
Uses 2 Mines, enter Left,Right,Down, Fire Machine Gun.Anyone that gets near it will be pulled in, and not likely to get out. The afterburner may get you out if you are pulled in. It lasts for about 5 seconds before the mine disappears.

Cactus Patch
Uses 6 Mines, lays a red flashing mine that will split when someone gets near it. It will lay the 6 mines in a group that can cause heavy damage if you drive over it. It is just 6 neatly placed mines. Great against tailgaters. Enter Left,Right,Up,then fire the machine gun to activate

After you enter the directional codes, you then must fire the machine gun (Z at default)