I think the new 300 is one of the best-looking cars out there. If I was currently in the market, it would be on the top of my list. I also like the Magnum. Wasn't too fond untill I saw one in person--pretty mean looking.
The Caddy sedan and that new roadster are also pretty sweet designs.
Pontiacs have always had too many plastic doo-dads on them for my liking--scoops/vents/flares.
Although, overall I think that recent American car designs are leaps and bounds ahead of 5 and 10 years ago when general blandness ruled.