Get the ATV :
At the Main Menu hold R1 and enter Up, Right, Down, Up, Right, Down. When you release R1 the screen will flicker to confirm correct code entry. Now enter any race and select any snowmobile, when the race starts, you'll have an ATV.

Get the Go-Kart :
At the Menu hold R1 and enter Right, Right, Left, Left, Right, Right. When you release R1 the screen will flicker to confirm correct code entry. Now enter any race and select any snowmobile, when the race starts, you'll have a Go-Kart.

Demo Mode:
At the main menu hold R1 and enter Up, Up, Up, Down, Down, Down.

Unlock All Snowmobiles, Tracks, and Leagues:
At the Main Menu Hold R1 and enter Up, Triangle, Up, Triangle, Up, Triangle.

Unlock Bonus Palm Track:
At the Main Menu, enter Hold R1 and press Triangle, X, Circle, Circle, X, Triangle. At the Track Selection Screen, pick Calgary.

Unlock Bonus Cartoon Track:
At the Main Menu, enter hold R1 and press Left, Up, Right, Circle, Triangle, Square. At the Track Selection Screen, pick Kiruna.

GameShark Codes

255 Championship Race Points
801fb77000ff 
 
Infinite Cash
801fb774e0ff
801fb77605f5  

Start On Final Lap
e012dcfa0000
3012dcfa0002  
 
Always Finish 1st
e012dcfa0002
3012dcfb0000
   
Unlock All Tracks, All Sleds, and Hill Climb Events
801fb1fc0007
   
Max Trick Cash
800C5aa0270f
   

Thanks to Revolution reader Frosty!