2: 1970 Marcos Mantis
There are quite a few sports cars that came out in the 1970s that didn’t deserve to see the light of day. The 1970 Marcos Mantis is one of these cars. The design of the car is bad enough, but performance was also lackluster at best. There was nothing remotely appealing about this car (via Hagerty).

Just the naming of the Mantis should have been enough to send drivers running for the hills. The car was perhaps one of the worst planned sports cars of the decade. Car enthusiasts who know their stuff try to avoid this thing at all costs. There is no value in the Mantis.