I've always thought a CTS-V would be amazing with AWD, especially if they managed to produce one that wasn't quite so heavy. I guess I would want a 2nd-gen CTS-V, AWD, 6-speed manual, with some kind of "track pack" option (less weight, more aggressive tune, a couple suspension tweaks). Paint it Nassau Blue (C5 color). It would be a hard choice between the coupe, sedan, and wagon.
In a fantasy "it would never happen" build, I would want a Holden Coupe 60 with an LSX454R (N/A) or some kind of custom LS-based setup (turbocharged). I would also want a late 70's Chevy crew cab 4x4 dually powered by a beefed up Duramax.