* Ford Mustang: Its introduction in 1964 sparked a pony car craze and remains incredibly iconic. Its affordability and sporty styling made it incredibly popular. This is probably the strongest contender for "most famous."
* Chevrolet Corvette: The Corvette's popularity continued to grow throughout the 60s, particularly with the Sting Ray model (C2). Its performance and stylish design cemented its place in automotive history.
* Volkswagen Beetle: While not new in the 60s, the Beetle's continued popularity and association with counter-culture made it incredibly recognizable and culturally significant.
* Ford Thunderbird: The Thunderbird, especially earlier models, retained a strong image of luxury and status.
The "most famous" ultimately depends on how you define fame. The Ford Mustang likely holds the edge due to its massive sales figures and immense cultural impact, but the others all played significant roles in shaping the automotive landscape of the decade.