I've had many favourites through the years and I think preferences change from time to time so my fave list probably won't be exactly as it is currentlly, say a year from now. Anyways, the cars on the list are in no specific order since I cannot tell which of these I like more than the others:
Futo - Fun and exciting little tuner, lots of customization options and it keeps you on your toes... Looks good and is never boring to drive around with.
Blista Compact - I don't generally like FWD cars but there's just something about this CRX screaming for attention. The sounds are great and the handling is top notch. It's just overall very fun to cruise around with, revving that engine and busting those corners in this retro nugget
Coquette - It's like an untamed cat beast. Super fast, lightweight, loud and aggressive. As with Futo, driving this car is very exciting and sobering, it's quite unforgiving but handling those corners and overtakes at top speed feels very rewarding.
Schafter V12 (Armored) - This car is 100% TCB and 0% bullsh*t. It's fast and reliable, handles better than most of the cars in the game, and being able to take 1 direct RPG shot without exploding (along with bullet resistant windows) makes this car one of the best all-arounders in my books. Not to mention it looks very good and elegant.
Warrener - Once again, looks very good, drives amazing. If you need a getaway car - search no more, you've found it. This car handles off-road and on-road with equal finesse. I love it.
PS. There are so many cars in this game I absolutely love driving around, I didn't mention a single muscle here even though most of the cars that I own belong to the muscle class. So as you might have figured out, I did have a hard time trying to think of what to list here because I have so many cars I like to drive around with.