It all depends on what you like, a Ferrari 360 running hard through the gears gives me the same chill bumps as a 10k RPM B-series at WOT.
Boris' e46 M3 sounds incredible.
Just about every time I drive my Integra someone tells me it doesn't even sound like a Honda...automobile that is.
LSX's with cam's, lightweight flywheels, and tuned exhausts are simply orgasmic.
Cleve's 996 GT2 with swirls of flames coming out of it gave me a chubby every time.
A Carrera GT with straight pipes has everyone beat for a street car, hands down. Too bad nobody I know of on the board has one! http://www.youtube.com/watch?v=Um2zNh8Wd9w