Venom bike:
Enter 68QCMH3H9HT as a password.

Wasp bike:
Enter 55HZ1MH3H9H1 as a password.

All Bikes:
Enter 3GP8ZKW76ZMW as a password.

Enter "Extreme Contest" mode and type the following as a name at the bike selection screen:

SPIRAL		Spiraling screen
SPYEYE 		Overhead view
MISPLACE	Misplace mode
XCHARGE		Infinite shields and primary weapon
MISTAKE 	Infinite weapons
NITROID 	Infinite turbos
NOPANEL		Remove all meters and text
2064    	Wipeout mode
XXX     	Turbo mode
FLICK   	Magnification mode
LINEAR  	Wireframe graphics 
PIXIE		Remove Fog
NEUTRON		Tron Mode
JUGGLE 		Juggle Mode

Neat Tricks:
Type RA50 as a name. And at any time during the race press Pause and select quit. Instead of quitting the race, the game will act like you finished the race. If you pause before the race starts, you'll get the first pole position. You can do this at any race without putting the code again.

Thanks to Revolution readers Rene Ellul, Kyle Greivenkamp, Sufyan, Bradley Kilgore, Cyborg, Jason Alvarado, Aaron, Daniel Chimene, Felipe Stefanini Rodigues, Brad Cason, Aylwin Villanueva and Damian!