Quality of the following is, of course, interpretive, but I include some here for the purposes of re-skinning, Frankensteining, whatever you want to call it.
Suspiria (1977) = witches
Wake Wood (2011) = careful what you wish for
Zombi 2 (1979) = adventure island
The House by the Cemetery (1981) = house by the cemetery
The Omega Man (1971) = Quevari? Vampyrs?
Soylent Green (1973) = societal horror
Pumpkinhead (1988) = curses/careful what you wish for
House of Wax (1953) = classic
Curse of the Werewolf (1961) = classic
The Devils (1971) = multiple themes
Taxi Driver (1976) and chased with Hardcore (1979) = urban debauchery/microcosm; no-name/"noir heroism"
Peter Cushing and Christopher Lee (in most everything they've done) = core RL archetypes
Hell Comes to Frogtown (1988) = good laugh
The Sandbaggers (1978-1980 TV) = Falkovnia-Darkon "Cold War" and the skullduggery behind it (including the signatories of the Treaty of the Four Towers for added depths of muckery)
And that's all for now. Maybe I'll add more. Maybe I'll forget about this thread. haha Either way, I've found inspiration through all of the above films. Skinning the ideas is a bit of an art, but it's easy enough for any DM to do I like to think. The last one, the Sandbaggers=Falkovnia-Darkon Cold War was a major campaign of mine. Trimmed with (eventually stripped-down) info I found in various books about the SOE..
"A very piteous thing it was to see such a quantity of dead bodies, and such an outpouring of blood - that is, if they had not been enemies of the Christian faith."
- Jean Pierre Sarrasin, "The Memoirs of the Lord of Joinville"