Beat the listed event in career mode or obtain the listed level to unlock the corresponding car. The invitationals require only podium (top 3) finishes.

Car	How to unlock
BMW M3 GT3 ALMS	Beat the Endurance Challenge of Champions.
Chevrolet Corvette Z06	Beat the Modern B Invitational.
Falken Tire Porche 911 GT3 RSR	Driver Level 15.
Lotus Elise	Beat the Modern C Invitational.
McLaren MP4-12C	Beat the Modern A Invitational.
Monster Energy/Falken Tire Ford Mustang GT	Beat the Drift World Championship.
NFS Shelby Terlingua Ford Mustang	Driver Level 11.
Team NFS BMW Z4 GT3	Beat FIA GT3 Championship.
Team NFS Mazda RX-7	Beat Works Championship.
Team NFS Mazda RX-8 Drift	Driver Level 5.
Team NFS RTRX Ford Mustang	Beat the Muscle World Championship.
Team NFS Time Attack AWD Scion tC	Beat Time Attack World Championship.
Team NFS Toyota Corrola AE86	Beat the Retro World Championship.