I hold a great personal fondness for Zardoz. It is annoying, boring, impenetrable, poorly acted, edited, scripted, conceived, and just monumentally miscalculated on every level, but I still don't like it on a purely ironic, "Plan 9 From Outer Space" level - it's so much more than that. I'm more just in awe of it, that something as weird and insane as it really exists. There are few modern precedents for it.
And also, of course, it's easy to appreciate just for it's frequent moments of pure, unadulterated surrealstic weirdness. I used to play the audio clip of "The gun is good! The penis is evil!" on my radio show all the damn time.
Also, and I can't stress this enough - naked horseback riding.
The last indie/artsy/foriegn film-centered video store in my town is going out of business and coming to the end of the long, painful process of selling off their old stock. I stopped in there a couple weeks ago to pick over the well-picked-over remainder of their stuff and say a fond goodbye, and picked up a $1 VHS copy of Zardoz. On my way out the owner told me to call him if I had any problems with the tape. I told him I'm sure the tape plays fine, but that doesn't mean it's problem-free by a looooong shot.