So what motivates your Mutant Future and/or Gamma World game?
I generally avoid the gritty Mad Max stuff in-favor of the weird and the exotic - plus some gratuitous kinky stuff. For my games, I like to find strange and interesting mutants and aliens, retro-styled technology, some steam-punk, worlds subject to cold war era styled nuclear apocalypse or social-decay. Social commentaries are quite common with post-apocalyptic fiction, so I put then in for traditional or comedic reasons (mostly comedic).
Books:
Armageddon 2419 A.D. - Philip Francis Nowlan
Barsoom saga - Edgar Rice Burroughs
Brave New World - Aldous Huxley
The Colours Out of Space - H.P. Lovecraft
The Lost Content (aka Beyond Thirty) - Edgar Rice Burroughs
The Last American - John Ames Mitchell
Orphans of the Sky - Robert A. Heinlein
Red Shadows, Slithering Shadows, etc. (anything with the strange green-stone cities found in the Conan yarns) - Robert E. Howard
Comic Books/Manga:
Axa
Comic book anthologies (Heavy Metal, 1984 (Warren), Epic, Witzend, etc. - these are mixed-bags of stories and genres)
Kamandi
The Last Generation
Magnus Robot Fighter
Mighty Samson
Nausicaä of the Valley of the Wind
The Savage Land
Warlord
Shows:
Highlander TAS
Thundarr the Barbarian
Movies:
Barbarella
Damnation Ally
Gandahar (aka Light Years)
Heavy Metal (Den and Taarna segments)
La Planète Sauvage (aka Fantastic Planet)
Logan's Run
The Omega Man
Sleeper
Westword/Futureworld
Zardoz
Update: added Woody Allen's 1973 film Sleeper. (It should be known that the "Pleasure Orb" also appeared in the 1st ed Gamma World treasure list - that list was full of easter eggs)