Personally, I think the coolest car ever is the 1954 Mercedes-Benz W196 R Stromlinienwagen (streamliner) race car designed by Rudolf Uhlenaut. It was driven by Juan-Manuel Fangio to win the world championship that same year.
It used an M196 R 2.496-liter Straight 8 (utilizing Bosch Direct fuel injection, like the 300SL Gullwing and used 2 valves per cylinder, DOHC, with desmodromic valve operation) engine producing 290 bhp @ 5800 rpm and 217 ft lbs of torque, and 116 bhp per liter. Top speed: 186 mph.
Sterling Moss driving a W196 R:
I could seriously imagine myself driving this thing on the street.