Thats a really hard question to answer, I love about as many cars as I hate others, I really love racing GT2/ GTE in AC and R3E sadly we´re still on old physics in R3E and they feel kinda floaty, but the Corvette C7R has to be one of my favorites of these, I´m also a big fan of Formula 3 in R3E and AMS, they are a bit twitchy but once you get the hang of them, they are amazing fun and super satisfying to drive.
Also the Minis in AMS are a lot of fun and provide some really good racing.
Lately I also found my love for Porsche in AC, the GT3 cup car gives you the possibility to have awesome same make racing with cars that are easy to pick up, but hard to master, the weekly Club races with them are just a blast (especially the last one on the Nordschleife
@Eugene Abramoff).
Overall I don´t think I have ONE favorite car, I just pretty much have a favorite car per class.
Raceroom GT3: Audi r( (hopefully we get the new one soon)
Raceroom GT2: Corvette
DTM: Audi RS5
90s touring cars: Mercedes 190E Evo2
Open Wheel: all the F3´s that I know
I really do enjoy Prototypes and multiclass racing, one of my favorite prototypes is the Mistral P1 in Raceroom.
And at the end I do also enjoy the KTM X-Bow in Raceroom, its something completely different to everything else in the game, but ince you got your head around it, you can just throw it around corners like nothing else in the game.
PS. I like racing (almost) everything thats not WTCC.
PPS. I´d love to see a few GT4 cars in Raceroom to have an alternative to WTCC.