From The Main Menu, Select Options Then Cheat Codes
(Case Sensitive)

dfens	              Agro (Special Move for SUVs and Trucks)
getheadl	          Bunny Ears (On MotorBike Rider)
haveyouseenthisboy	Chrome Body
urbansprawl	        Faster Pedestrians
trythisathome	      Flaming Head (On MotorBike Rider)
hyperagro	          Increase Car Mass In Arcade Mode
ontheroad	          No damage
getheadk	          Pumpkin Head (On MotorBike Rider)
RO4r	              Roar (Special Move for Choppers and Muscle Cars)
getheadn	          Skull Head (On MotorBike Rider)
getheadj	          Smiley Face (On MotorBike Rider)
getheadm	          Snowman Head (On MotorBike Rider)
roadtrip	          Unlocks All Cities in Arcade Mode
crosscountry	      Unlocks All Cities in Arcade Mode
allin	              Zone (Special Move for Sport Bikes, Tuners and Exotics)


Unlockable vehicles

To unlock the following vehicles, complete the following:

Hummer H3T	           Beat the Big Playas Tournament
Nissan Sport           Concept	Complete the Class C vehicles Only tournament.
Paul Smart Sports Bike Beat the Original Riders Tournament

Unlockables in Tokyo

Beat the following tournaments in Tokyo to unlock.

Chevy Cobalt SS	 - Beat Unbeatable Street Racers tournament.
Gemballa F355	   - Beat By Invitation Only tournament.
Hotmatch Chingon - Beat Choppers Of America tournament.
Tokyo Police Car - Beat the entire challenge