Unlock All Cars and Tracks  -  Enter 29801 on the code screen, and all cars and tracks will be unlocked.

Unlock the Game Stop Car  -  Enter 07913 on the code screen, and you will unlock the Game Stop Car.

Unlock the Master Car  -  Enter 62972 in the code screen and you will unlock the Master Car.

Gameshark Codes

Must Be On [M] 56C31161DF750EFC   EB9860C6C2960A13
Press GS Button For More Time 0665ACA597AF1FCA 
Low Lap Time 8FF6A806BB9B7FA5 
Invincible C4709550144223FA