@Wolf - actually, thinking about it, if it had been done in one take, wouldn't the actors have to absolutely nail it with no mistakes? Seems hopeful.
@Imami - I haven't seen 2046 yet. Looking forward to it though!
OK this isn't
that obscure but it certainly deserves more recognition outside of the film community.
Peeping Tom

It wasn't received at all well in the UK which all but ended the career of director Michael Powell. It has many similarities to Hitchcock's Psycho (which came out three months later) - both about a serial killer with parental based obsessions - but has forever been overshadowed by it.
It has since been re-evaluated and is now on all kinds of 'greatest films' lists but, imo, still doesn't get the respect it deserves.
It's better than Psycho and you know how people juice themselves over that!
- "Peeping Tom is a chilling, methodical look at the psychology of a killer, and a classic work of voyeuristic cinema."
That, basically.