Seriously bizarre movies

Most of these directors and films fall into the category of experimental, but they will expand your mind and perception of cinema nonetheless.

Filmmakers:
Guy Maddin
Kenneth Anger
Chris Marker
Jan Svankmajer
Craig Baldwin
Stan Brakhage
Apichatpong Weerasethakul
Paul Morrissey


Films:
Big Man Japan
The Ruling Class
House
Heaven and Earth Magic
Meshes of the Afternoon
Wavelength
Performance
The Man with the Movie Camera
Repulsion
Dogville
Europa
The Kingdom (Technically a miniseries, but well worth your time. It is a towering work of modern surrealist cinema.)

Also I could not agree more with Werckmeister Harmonies Bunuel recommendation, although if you are looking for his most bizarre film, try either Un Chien Andalou or L'Age d'Or. As a matter of fact, also watch Werckmeister Harmonies by Bela Tarr.
 
Try Andrzej Zulawski's Possession, it is a strong contender for the most thoroughly "metal" film ever made. It is a psychological/body/supernatural horror film that pits Sam Neill and Isabella Adjani against one another in a disturbing battle of wills. When Neill obtains custody of his child and notices his wife is neglecting her maternal duties due to an increasingly ferocious emotional and spiritual funk, he attempts to reconcile. This only leads to his immersion into her bizarre world of psychotic hallucination. From there we find ourselves witnessing events ranging from tentacle rape to the unspeakable to the unfathomable.
 
Not on the same plane as some of those already listed but :
Russ Meyer's 'Up'
Boobs and Nazis. And more boobs.
The Monkees 'Head' is also a tad on the strange side.