20: Plymouth GTX
Plymouth was also a heavy hitter during the muscle car era, with many great models that we remember. The GTX is sort of a lesser-known model that still offers a great amount of value. The styling of the Plymouth GTX is very memorable, and the car has a lot of potential for classic muscle car collectors (via Hagerty).
The Plymouth GTX was one of the most unique Plymouths that hit the market during this period. Performance was top of the line and the rarity of the car makes it unique. Most automotive enthusiasts have forgotten this car existed, but it was an integral part of the muscle car era.