I'm a huge fan of a certain sort of rock music that goes so far out into experimental, weird territory that it sometimes just barely qualifies as rock music at all. It's music that takes the concept and techniques of psychedelia to an extreme. Often various non-rock influences will be mixed in (most commonly musique concrète) to give the music a special texture or vibe. I don't mind if the music is difficult or avant-garde.
I dig interesting and lush production, but I don't mind standard or even poor production. I also dig really varied, interesting instrumentation.
Bands that express the qualities I'm looking for:
The Olivia Tremor Control
(and much of Elephant 6)
(especially the song "The Owl Service," which isn't on youtube)
"Tomorrow Never Knows"
by the Beatles
Porcupine Tree (especially songs like "Drown With Me"
and "Stars Die"
Brain Eno's album "Another Green World," especially the song St. Elmo's Fire
Boards of Canada
(though they're not really rock)
And to a lesser extent:
Radiohead's album "Kid A"
dredg's album "el cielo"