As you progress through the game you will challenge the 5 Kings (Showdown, Drag, Drift, Grip & Speed). When you beat each of them you will get their car as a reward.

Unlock 1965 Pontiac GTO (Nate Denver):
Beat Speed King in Career mode.

Unlock 1995 RX-7 (Aki Kimura):
Beat Drift King in Career mode.

Unlock 2006 Mustang GT (Karol Monroe):
Beat Drag King in Career mode.

Unlock 2008 Evo X (Ryo Watanabe):
Beat Showdown King in Career mode.

Unlock 2008 M3 E92 (Ray Krieger):
Beat Grip King in Career mode.

Go to 'Options' and then 'Career Mode' and enter the following case-sensitive code without the quotes at the 'Enter Code' menu. Some of these codes can only be used once so it is advised that you disable the 'Auto-Save' option so you can revert the game back to it's original setting.

Unlock Everything in the Game:
Enter the password 'UNLOCKALLTHINGS' to unlock ALL maps, cars etc.

Unlock ALL Bonuses:
Enter the password 'MASTERCODE' to unlock ALL the bonuses in Career mode.

Unlock Audi TT 3.8 Quattro:
Enter the code 'ITSABOUTYOU' to unlock the Audi TT 3.8 Quattro in Career mode.

Unlock Chevelle SS:
Enter the code 'HORSEPOWER' to unlock the Chevelle SS in Career mode.

Unlock Coke Zero Volkswagen Golf GTI:
Enter the code 'ZEROZEROZERO' to unlock the Coke Zero Volkswagen Golf GTI In Career mode.

Unlock Energizer Lithium Dodge Viper SRT10:
Enter the code 'WORLDSLLONGESTLASTING' to unlock the Energizer Lithium Dodge Viper SRT10 in Career mode.

Unlock Mitsubishi Lancer Evolution:
Enter the code 'MITSUBISHIGOFAR' to unlock the Mitsubishi Lancer Evolution in Career mode.

Unlock Castrol Syntec Decal:
Enter the code 'CASTROLSYNTEC' to unlock the Castrol Syntec decal in Vinyls.

Unlock Energizer Lithium Decal:
Enter the code 'ENERGIZERLITHIUM' to unlock the Energizer Lithium decal in Vinyls.

Unlock 5 Free Repair Markers:
Enter the password 'SAFETYNET' to get 5 free repair markers in Career mode (this password can only be used once).

Unlock Extra $2,000:
Enter the code '1MA9X99' to get an extra $2,000 in Career mode (this password can only be used once).

Unlock Extra $4,000:
Enter the code 'W2iOLLO1' to get an extra $4,000 in Career mode (this password can only be used once).

Unlock Extra $8,000:
Enter the code 'L1iS97A1' to get an extra $8,000 in Career mode (this password can only be used once).

Unlock Extra $10,000:
Enter the code 'CASHMONEY', 'REGGAME' or '1Mi9K7E1' to get an extra $10,000 in Career mode (this password can only be used once).

When you have a Need For Speed Carbon memory save on you PS2 you will receive a bonus of 3 extra Repair Tickets and a Total Repair ticket. You will also receive a message on your screen thanking you for playing previous Need For Speed titles.