Cheat Most Wanted Black Edition

Here it is Cheat for Most Wanted Black Edition :

You can enter those CHEATS at the "Press Enter" menu. 
The acuracy of these codes has not yet been confirmed, so test away. 

Note that not all of these will work in Career Mode. 

Code                Result
--------------------------
castrol           - Exclusive ford GT
burgerking        - Unlock bugerking challenge
regmebaby         - Gives you 20,000 in career mode to start 
opendoors         - Access to whole driving world 
ordermybaby       - Access to all cars 
gimmevisual1      - Unlocks Visual Upgrades Tier 1 
gimmevisual2      - Unlock Visual Upgrades Tier 2 
needperformance1  - Unlocks Performance Upgrades Tier 1 
needperformance2  - Unlocks Performance Upgrades Tier 2 
goforoldspice     - Unlocks Old Spice Vinyl 
needmybestbuy     - Unlocks Best Buy Vinyl 
gotmycingular     - Unlocks Cingular Sponsor Vinyl 
gottahavebk       - Unlocks Burger King Vinyl 
gottaedge         - Unlocks Edge Sponsor Vinyl 
davidchoeart      - Unknown 
shinestreetbright - Unknown 
wantmyd3          - Unknown 
wannacapone       - Unknown 
gimmechingy       - Unknown 
yodogg            - Unknown 
tunejapantuning   - Unknown

source : http://www.cheatbook.de