I have many but did no one really mention Porsche?

Single turbo'd Supras and Skylines make the hair on my neck stand up.

Volkswagen R32 is the best sounding V6 IMO 2nd is the Nissan VQ35DE

E36 M3s can sound very nice. Muscle cars and Ferrari/Lambo/etc. are a given.

I personally think the WRX sounds like a big ATV or something but it doesn't really matter what it sounds like when it makes power IMO (eg: RX7's).