5. Soylent Green (1973)
Though nowadays it's mostly famous for the SNL sketch that saw Phil Hartman as Charlton Heston screaming "It’s People!" and giving away its twist, Soylent Green is actually a great, underrated movie. The film depicts an overpopulated New York City where the greenhouse effect has led to rampant poverty and constant humidity. Meat is extremely scarce, so people survive on processed food — one of them being Soylent Green, a delicious substance with a curious aftertaste made from "high-energy plankton." In Martin's opinion, it's one of the post-apocalyptic genre's best. "It was extremely realistic, and way before its time. In my book I describe types of meat and their nutritional value, and human meat — putting aside all the moral and ethical societal locks that they put on it — is very nutritious, especially human meat that's not filled with all the preservatives and chemicals that we're being fed now."