Use Big Game Mode to finish all the races to get 2 new bikes capable of 300mph+
Get Scooters
At the main menu press C-Down, C-Right, C-Up, C-Left, Z, Z, L, C-Left.
Infinite spikey clubs in Big Game mode
For some strange reason, if you type in the All weapons code (C up x4, c down, L, c left, z) and go into Big Game, you will have unlimited spiked clubs. This enables you to continually use them to jam people over and over until you turn the game off.
Insanely Fast Bikes
At the main screen put in Up, C-Left, C-Left, C-Right, Left button, Right button, C-Down, and Z.
Insanity Level
At Thrash Mode press C-Up, C-Left, C-Left, C-Right, L, R, C-Down, Z.
Stages
Stage 2:
At the main menu, press R, C-Right, Z, R, L, C-Up, C-Left, C-Up.
Stage 3:
At the main menu, press R, C-Right, C-Right, C-Right, R, C-Left, C-Down, Z.
Stage 4:
At the main menu, press R, C-Right, C-Down, C-Left, C-Right, C-Right, Z, L.
Stage 5:
At the main menu, press Z, C-Right, C-Down, C-Left, C-Right, C-Right, Z, L.
The Mystery Level
Get at least 52 batteries and assault a cop 19 times in the insanity level,stage 2. You'll hear a chime at main menu press c-up c-down(2x) z z R L L c-down c-right FAST. You won't hear a chime this time go to level 5 get 52 batteries in stage 5 and you'll get the code. Its tricky but you'll get it after the first 10 times, don't lose patience.
Turbo Start
Hold down A when the race starts for a turbo start.