I have a 78 Magnum GT and a '71 Challenger 440 6 Pack, so those are my 2 favorites, in the same vein as if someone asks you which of your kids is your favorite!
In fairness, the question would be better if it was what is your favorite post 70 Mopar design, as the E bodies and A bodies where effectively carry over 1970 designed cars with a few cosmetic changes.
Phrased that way, then I could say the Magnum.
Others that intrigue me would be a one of the handful of Miradas made with the E58 engine before they realized they didn't meet EPA standards and canceled that engine option, the 71 Roadrunner or GTX, a late 70s powerwagon, and the Supercoupe with T Tops.
View attachment 1531157