Successfully complete the indicated task to unlock the corresponding car:

Assassin Sports Car: Get 100 Takedowns.
Custom Sports: Win the Gold medal at the Airport Race.
Dominator: Get 60,000 Burnout Points.
DX Sports: Win the Gold medal at the Downtown Eliminator.
Legend Racer: Win the Gold medal at the Downtown Legend Face-Off.
Legend Roadster: Win the Gold medal at the Silver Lake Legend Face-Off.
Legend Special: Win fifty five Gold medals.
Modified Sports: Win the Gold medal at the Island Paradise Race.
Sports Cop: Win the Gold medal at the Golden City or Island Paradise Pursuit.