Unfortunately, in my experience, some of the coolest looking ones also have the worst ergonomics (such as the Werra).
Leica LTM, it's various clones and Leica M definitely have an adavantage in sheer usability over most other classic ones (not talking about recent ZI or Bessas).
But the Werra, Retina IIIS, a number of Voigtländers and other Retinas, the more advanced Braun Paxettes and the Soviet Leningrad definitely have a high "cool" content.
In the LTM clone world, the Zorki 3 also looks great (and tends to be well-made as well).
P.S, Arrrgh! Forgot the Contax and its clones... Though the ergonomics caveat applies strongly here as well...