Start game, go to the main menu, go to the Statistics sub-menu, go back again (pressing backspace), and finally enter your desired cheat:

• 111skyline - unlock Skyline
   
• 119focus - unlock Focus
   
• 221miata - unlock Miata
   
• 222lancer - unlock Lancer 
   
• 334mygolf - unlock Mygolf 
   
• 350350z - unlock 350Z 
   
• 371impreza - unlock Impreza 
   
• 667tiburon - unlock Tiburon 
   
• 777rx7 - unlock RX7 
   
• 77peugeot - unlock Peugeot
   
• 893neon - unlock Neon 
   
• 899eclipse - unlock Eclipse 
   
• 922sentra - unlock Sentra 
   
• gimmeppablo - unlock Petey Pablo 
   
• gimmesomecircuits - unlock Circuits 
   
• gimmesomedrag - unlock Drag Circuits 
   
• gimmesomesprints - unlock Sprint Circuits 
   
• gotcharobzombie - unlock Rob Zombie 
   
• havyamystikal - unlock Mystikal 
   
• needmylostprophets - unlock Lost Prophets 
   
• allmylvloneparts - unknown Effect
   
• allmylvl2parts - unknown Effect
   
• seemylvl2parts - unknown Effect
   
• driftdriftbaby - unknown Effect
   
• slidingwithstyle - drift style in all races
   
• givemenismo - unknown Effect

by NFS Unlimited - www.nfsunlimited.net