Here's a much better list of 50 vehicles (as they didn't stick to just cars) in my opinion, in alphabetical order:
AC/Shelby - 427 Cobra, Daytona Coupe
AM General - Humvee
Aston Martin (in general, except for the Cygnet, I mean come on)
Audi - R8 V10
BMW - Z4 M Roadster
Bugatti - Veyron
Carbon Motors - E7
Chevrolet - C5 Corvette Z06
Dodge - ‘69 Charger, Charger (LX, 2012+), Viper
Ferrari - 308 GTS, F40
Ford - Excursion, Ford GT, GT40, Mustangs (Boss 302, Boss 429, Mach 1, Shelby GT350, Shelby GT500, 2000 SVT Cobra R), SVT Raptor, Taurus SHO (4th gen), Thunderbird (1st gen), Torino (‘70+), TS50
GMC - ‘A-Team’ van (original)
Honda - NSX
Jaguar - E-Type, XJR-15, XKR (X100)
Koenigsegg - CCX
Lamborghini - Countach, Diablo SV, Murciélago SV
McLaren - F1 GTR
Mercedes - CLK GTR, SLR McLaren
Nissan - GT-R
Pagani - Zonda
Pontiac - ‘77 Trans Am Special Edition
Porsche - 550 Spyder, 911 Turbos (‘98+), 918 RSR, 959, GT1-98
Various - M3 Half-track, M35 ‘Deuce and a half’