I think the 370z should be out of the running since we are a little biased and its pretty much a given.
For around $70k or less and judging purely on cosmetic.....
1. Jaguar XJ
2. Porsche Cayman R
3. Alfa Romeo 4c (Not currently in production just yet though)
Runner up's
-Audi TT RS
-Mustang Boss 302
-BMW M3