21. Marcos Mantis
Marcos is a small English company dedicated to building sports cars with components borrowed from other brands. But in 1968, they wanted to expand and offer a luxurious GT. The Mantis came with a Plexiglas body, 2.5-liter straight-six engine, and more interior comfort.

The idea was great, so the company came up with a cool name. But unfortunately, the design was hideous. In the early days of composite materials, the design was much dependent on manufacturing technology. And that is why the Mantis was an ugly, almost scary sports car.