There are 2 movies I think about when I come across this type of question. A good friend of mine who was a big movie buff/snob recommended them to me when we were in college. I'm interested to see how obscure you guys think they are.
Apartment Zero: some of the darkest comedy I've come across, some great characters and a pretty good story as well. It also put Buenos Aires on my list of places I'd like to visit someday.
Metropolitan:
Mansfield Park meets late 80's Manhattan. This is a real love it/hate it type of movie. If you don't know who Jane Austen is you'll probably fall in the latter category.
If Harold and Maude qualifies as obscure then
Blue Velvet deserves a mention as well. I realize it was relatively big in its day and made a lot of critics top movies of the 1980's list, but I occasionally throw some pop culture trivia in on rounds with my medical students/residents and am constantly surprised at how many of them have never heard of it.