For looks, my favourite car is a stock-bodied gold
2000GT'68.
Based on statistics, my favourite car appears to be the
1993 Supra (turbo).
Embarrassingly, the
Cultus PPV appears quite soon after that in the number of races entered.

Oh... I would use it to make money at
Red Rock. And in my first game used it to collect the
Rally Cups.
Close behind that are the
TVR Speed 6 and
Speed 12. And then, surprisingly, comes a
tunedMini, i.e tuned
Mini Cooper 1.3i used a lot in my first game for the lightish car races.
But off-the-top-of-my-head one of my favourite cars for driving is the
Mine's Lancer Evo V, even if the game doesn't know quite what its drive-train is...
Edit: Actually, I didn't use the Cultus quite as much as I thought. Problem is I duplicated my records for some games which are really just "car-saving garages" and so counted a lot of those races multiple times. In face the Speed 6 and the Supra'93 appear to be about tied for first, with the Mines Evo V close by next.