I've been spending alot, I man ALOT, of time recently driving an Audi TT 3.2 quattro. I adore this car in real life, always have. I remember when I first earned enough credits in GT3 to buy a car beyond the Vitz I bought a Audi TT. I then remember being disappointed. The TT in GT3 was sorta useless. It's stock form was a mess and even when tuned it had no real use beyond the TT race. It was a pig.
Well. In GT4, PD really outdid themselves with the new 3.2 quatto TT. In it's stock for it is absolutely perfect. It sounds amazing and handles even better. Upgrading some engine parts (cluthc, flywheel, etc) really makes the most of it 250'ish PS. Sport suspension and lightweight upgrades take it another step further. This little car is on my top 5 cars in GT4, it took out a RUF to do that too....
I'm a Porsche/RUF fan primarily, but following that I love Audis. Interestingly enough I don't go for their bread and butter cars (the A/S4, RS6, A6, A8...etc). But I love their "little" cars, the TT and the new A3...not to mention their race cars!
My top 5 cars in GT4 thus far at 50.7% complete and over 120hours of play;
1) RUF Yellowbird CTR
2) VW GTI '05
3) RUF BTR
4) Nissan Skyline R34 v-spec II N1 '00
5) Audi TT 3.2 quattro
Honorable mention;
Audi A4 DTM, Audi R8, RUF 3400s, Lotus Elise 111r, Amuse s2000, BMW M3 GTR (race car), BMW M3, Nissan Z (GT edition), VW Karramn Ghia, Falken GTR