The sportiest car I've ever owned was the GTI. Manual tranny, plenty of power (for me), good mpgs, good handling, little understeer. Those hot hatches combine a lot of fun with a practical design. Second would probably be the 2005 CTS, good power, RWD which led to some oversteer at times, automatic tranny, good handling.
I've driven sports cars, Porsche 924 included, a Ferrari, Mustangs of various ilks including the "II", a CTS-V on a track (that really is a sports sedan of course), an Austin Healey (I barely fit), probably a few others. I think my sports car days are well in the rear now though at times I muse about a Mustang GT convertible with a 6 spd.