My favorite car? Whew, that's a tough one. I like lots of cars. I'll break them down into classes and see if I can pick out my favorites from them:
C4:
Lancia Delta: Decently fast, grippy and can go off-road. THE car to get at the start IMO.
C3:
Corvette C1: I like American cars, this one is good for kicking back and relaxing.
Charger R/T: True example of a muscle car, and also DAT HORN!
308 GTS: One of the fastest cars of the class, a true performer. P.I. Magnum bonus points as well...
C2:
250 GTO: VERY rare. $5,000,000 pricetag ought to blow your mind. No wonder I haven't seen one on the roads!
Cobra Daytona: Good alternative to the 250 GTO and can be had for free as long as your exploration skills are up to scratch.
C1:
F40: Well, I don't suppose I have a choice, do I?
B4:
Range Rover: Muscular, stylish, no-one will mess with you.
Touareg V10 TDI: Big diesel engine offers plenty of torque, quiet and refined for cruising, but also a good choice for racing.
B3:
Q7 V12 TDI: Pretty much an upgrade of the Touareg above.
ML63 AMG: Cheapest of the class and with commendable performance.
B2:
Stratos: Pulls off the rally car feel better than any other.
A7:
Brera Italia Independent: Good power for the class and a glorious V6 engine sound.
MiTo QV: Not as fast as its big brother but agile in the turns. Also pulls off the mini-8C look rather cutely.
A6:
Camaro LT: I have a soft spot for American cars, the V6 Camaro is cheap with decent performance and a good choice for cruising.
Impreza STI: Without a doubt, one of the best all-rounders in the game. Great performance that can win A6 with ease, off-road ability to rival the best of SUVs and a nice burbly boxer-4 sound with turbo overboost. An Impreza should be in the garage of every TDU2 player.
A5:
RS5 Coupe: A nice choice for cruising and an upgrade over the S5 that shouldn't be missed.
TTRS Roadster: Very easy to drive, a pocket rocket.
Charger SRT-8: One of the fastest of the class on the straights. Turning's not very good though...
Mustang GT: Another good choice for cruising, if you can get over the single exhaust...
A4:
V8 Vantage: The vehicle that got me through the A4 class. Good speed (although not as much as the DB9s) and great agility. Also used to have a beastly backfire sound.
RS6 Avant: Come on, a WAGON keeping up with European exotics? That'll earn a spot in my list alone, never mind the twin turbo V10...
Camaro SS: Another American. Little outclassed by the Aston Martins, but good for cruising and very cheap (Less than $40,000!).
A3:
DBS Coupe: Fast, good handling, a good choice for long drives and rather expensive. James Bond chooses well.
CSR 260: When the going gets twisty, the Caterham shoots ahead of everything else this side of an Atom.
California: Likely your first Ferrari in the Asphalt class, and a good one at that. Race your way to victory, and then drop the top for relaxing in the sun.
A2:
R8 Coupe: Fast and grippy, the R8 is on your side.
Corvette ZR1: Pretty much anyone who is American should love the Corvette...
Viper SRT-10: ...And if not? The Viper is a powerful beast that does not suffer fools gladly. The base model is good, the ACR brings better handling and a massive wing, the Police model is a good off-road and pursuit car.
458 Italia: One of the best performers of the class, the Italia got me through A2 pretty much single-handedly. Also less of a mosquito than the 430 Scuderia...
SLS AMG: More of a cruiser than the 458, nonetheless it still has enough power for when you want to play.
GT-R: Performance on the cheap (Less than $100,000) and with enough grip to get you through a mountain pass. Also, anyone who loves turbo whistle shouldn't miss this one.
A1:
Atom 500 V8: Accelerates like a rocket, turns like a toy car and not too bad on the top speed front too.
One-77: Not the fastest, but this million-dollar Aston is still awesome. One of the cars which I feel captures the high-roller feel of TDU2 best.
Veyron SS: Yes, call me a noob. The Veyron has brilliant speed and acceleration, and is an ideal choice for when you want to get somewhere fast. The Super Sport is even faster, making it my choice. Unfortunately, it is forever marred by the reputation of being the rammer's ride of choice.
CCXR Edition: My designated Veyron killer and probably one of the only vehicles that can match the Bugattis at their game. Only thing is, it costs more than $2,000,000, and handling 1,000 horsepower through only the rears is not for the faint-hearted!
SLR Stirling Moss: Come on, a 200mph speedster with no roof and what you wouldn't even consider windshields? How's THAT for wind in yer hair!?
Zonda Cinque: If you don't get goosebumps from the million-dollar-pricetag or the fact Pagani only made 5 Cinques IRL, you will from the way this Zonda grips the road. If you want a Zonda and can afford this, then buy it.