My absolute favs are as follows, in no specific order.
Amuse 380 Supperleggera, maybe my fav.
Amuse S2000 GT1 '04, handles AMAZING!
Renault Clio v6 '00, an amazing hot hatch, total blast to drive.
Nissan 370Z, I own one in real life and its awesome in the game.
Gran Turismo 350Z, again, handles AMAZING!
Lotus Evora, a simply beautiful car that when tuned right lays everything to waste.
Thats just a few of my favs. Im not really into race cars thats why you dont see any up there. I do enjoy the older Mercedez tourning car and that new GTR that came with the update is pretty nice too.