Brandon K sends us the 1961 Fiat 600D Pininfarina Y Berlinetta (also known as the Berlinetta Aerodynamica Modello Y) - a unique aerodynamic one-off concept car built by Pininfarina utilizing a rear-engined Fiat 600D platform.  Following Pininfarina's radical 1960 Project X aerodynamic study, the Model Y served as a more realistic evolution focusing on high-efficiency body shapes, low drag, and directional stability.  Styled largely with input from Professor Alberto Morelli, it featured a compound-curved wraparound windshield, enclosed headlights behind a protective plastic shield, and distinct teardrop proportions.  Early iterations included rear stabilizing fins which were later shaved off for a cleaner look.  Pininfarina integrated early safety concepts into the cabin, using energy-absorbing materials and placing the spare tire ahead of the passenger compartment to assist with frontal collision impact absorption.  The car is now housed in the National Automobile Museum in Reno, Nevada.
More pics and information here