Enter GUARDIAN as a code.

Put in the code TRACTION

On any level during racing pause the game and HOLD L
  and press B, Y, Y, B, Y, X

Put in the code MARTIAL

On the Enemies Vanquished level during racing  pause the game and HOLD L and press X, X,
B, B, Y

Put in the code PARADISE

Put in the code MIDAS

Put in the code BOOM

Put in the code ASSASSIN

Enter TNT as a code.

Put in the code MELTDOWN

Pause the game, then enter any of the following cheats (NOTE: all of these cheats work
only in vehicle mode, and some of them work only on certain vehicle mode levels): 

  2X Armor: Hold down L and press X, Y, B, 2(X). Then release L. 
  3X Armor: Hold down L and press X, Y, B, 3(X). Then release L. 
  4X Armor: Hold down L and press X, Y, B, 4(X). Then release L. 
  Apline Race: Hold down L and press 2(X), 2(B), Y. Then release L. 
  Berserk mode: Hold down L and press B, 2(Y), B, Y, X. Then release L.
  Cobra: Hold down L and press 2(right), 2(left), up. Then release L. 
  Frantic mode: Hold down L and press B, Y, X, B, Y, X. Then release L. 
  Racing Trails: Hold down L and press B, 2(X), B. Then release L. 
  Super bullets: Hold down L and press 4(X). Then release L. 
  SUV: Hold down L and press B, X, Y, B, Y. Then release L.

Enter GAMEROOM as a code.

Put in the code Q LAB  (Must have
  the space)

Put in the code VACUUM

Put in the code TEAMWORK

On the Enemies Vanquished level during racing
  pause the game and HOLD L and press Right, Right, Left, Left, Up