Nostalgia race Volkswagen Beetle at Prague, great combo, funny car and best in FM5 track.
Lamborghini Diablo SC at rainy Batrhurst 
I wish this track got more elevation changes like in other titles.
Lexus LFA at new Yas Marina track all races with Thrustmaster TX wheel. Somehow LFA works better, more like supercar in FM4.
Ferrari 360 Challenge Stradale Sebring , nicely refreshed track, cars maxed to A700 class. At 3:00 sound bug can be spotted.
Ford GT40 old Le Mans , nice ride, but like most stock cars needs badly less understeer (easy to get with setup). Track looks beautiful, but already outdated without changing weather or day cycles, king of encdurance tracks and non stop same clouds? Nah, but… FM6 is coming
Viper SRT10 Road Atlanta , i miss so many tracks in FM5, luckily Road Atlanta is still there.
Subaru 22B at Catalunya
and Evo 6