Director: Andrzej Żuławski
Running time: 123 minutes
Where you can watch it: YouTube
Why it's unavailable: Shot in Berlin during the days of the Wall, Andrzej Żuławski's horror picture generated controversy for its politics and gruesome content. It was the grisliness that saw it released in America in a heavily edited, 97-minute-long version. Prints of the uncut, two-hour version have screened in the States, but you'll need YouTube to watch the definitive version in your home.
Why you should watch: Because it's that all too rare horror movie with a guiding idea beyond simply scaring the viewer. Possession, starring Jurassic Park's Sam Neill and Isabelle Adjani, is really about the collapse of a romantic relationship. If you've been close to a divorce, this movie is going to be scary for reasons that have nothing to do with the gooey creature.