Jeanne Dielman, 23 quai du Commerce 1080 Bruxelles. Granted, what I know of your tastes don't really suggest this would be up your alley, plus it's very long. But it's a unique and important feminist film and is cleverly executed, with a great lead performance from Delphine Seyrig.
La Jetée. This one's short so there's no good reason not to watch it. You may well know how the plot goes if you've seen the mainstream movie that's a loose adaptation of it, but it's still a striking and unique movie.
Last Year at Marienbad. I remember liking this a lot, though perhaps it's a bit one-note. But it's a good note.
The Spirit of the Beehive. I think I liked this,
but I barely remember it.
A Matter of Life and Death. Powell & Pressburger did at least five movies better than this one. It's still maybe worth a watch for some of the afterlife imagery, or if you're a David Niven fan.
Sans Soleil. I found this uninteresting and barely remember it.