At the name selection screen, enter (one of the cheats below):

 Code              Effect             
BIG CHEAT          All cars and tracks selection screen, enter  
LEAGUE CHEAT       All cars in Demolition Mode

Thanks to Revolution reader Fedrico Ferrari 84!

Codes

DWANZIL – More End of Race Points

Semi-Pro League Unlockables

Chicken (Game Mode) – Complete Semi-Pro League

Hunter's Quarry (Track) – Complete Semi-Pro League

Meltdown (Track) – Complete Semi-Pro League

Pelton Stadium (Track) – Complete Semi-Pro League

Predator (Car) – Complete Semi-Pro League

Pro League (Game Mode) – Complete Semi-Pro League

Scrap Heap – Complete Semi-Pro League

Rookie League Unlockables

Chase (Game Mode) – Complete Rookie League

Lyon Staium (Track) – Complete Rookie League

Mantis (Car) – Complete Rookie League

Renegade (Car) – Complete Rookie League

Semi-Pro League (Game Mode) – Complete Rookie League

Pro League Unlockables

Chemical Plant (Track) – Complete Pro League

Go Cart Carnage (Track) – Complete Pro League

Redneck Raceway (Track) – Complete Pro League

Endurance League Unlockables

All Reverse Tracks – Complete Endurance League

Vandal (Car) – Complete Endurance League

Arena League Unlockables

Suicide (Game Mode) – Complete Arena League

Widowmaker (Car) – Complete Arena League