46: 2015 Chevrolet SS
GM tends to drop the ball and that was the case with the Chevrolet SS. The sedan was based on the outgoing Pontiac G8 platform and its exterior styling was bland. Considering how much horsepower was under the hood, the SS didn’t look the part at all (via Car Talk).
It also didn’t help things out that GM rarely advertised the vehicle, so most consumers didn’t even know that it was on the market. The SS was more of a halo car than anything, and the model was phased out within a few years.