Rashomon: A rape and a murder and four versions (including one from beyond the grave) which agree only about the rape and the death but in all other aspects troublingly different. The realism of cinema given the Hiroshima treatment.
Eraserhead: Truest to the imagination of its author that I know.
Dark Star: Made for a vanishingly small fraction of the budget of the nearly contemporaneous Star Wars but with far more depth, real humour and intellectual content. And when it's cute it remembers that it should also be funny.
Boogie Nights: Multi-threaded compound narrative set in the porn industry but made as a celebration of family values. Everyone's good in it. Not P.T. Anderson's first but his debut on the world's screen. This created his fans-for-life-base.
2001: A Space Odyssey: My favourite Kubrick. From the dawn of humanity to its transformation into star children. Remembered to suggest that space travel, for all its pioneering constant moment, might also be boring. Was celebrated thus: "the next film set in space will have to be shot on location". Didn't happen but we are compelled to understand and to forgive.
The Haunting: When I compile these lists I think of all time favourites but only pick those closest to my memory. This doesn't just mean films I've seen recently but any title that comes up when I think of movies I like. That's why the lists are always substantially different from each other. This one keeps appearing in the lineup. It's just that good.
Monty Python and the Holy Grail: Still makes me laugh ... a lot.
Suspiria: Horror tale understands essential component of good horror: remove the control from the audience. It only fails when it tries to explain itself. Seen recently with a live soundtrack played by the band that wrote the music. Outstanding!
In The Company of Men: Inspired by the cads and machinations of Restoration comedy, this severe morality tale was neither bettered by its writer director nor anyone else for understanding male competition. The winner wins without penalty and this will make your heart sink.
Martin: Is he a mixed up kid who thinks he's a vampire or a vampire who will forever be a mixed up kid. Again, George Romero changed the game with a particular genre just because he could. The big budget world could never compete with the pluck and candour of this.