Hmm. There are great films that are off the beaten path, but you are probably familiar with.
Jodorowsky's "El Topo", "Holy Mountain", or "Santa Sangre" are equally amazing in their own distinct way.
David Lynch's "Mulholland Dr." isn't for everyone, but I find it constantly fascinating. I love Lynch anyway, and I think "MD" is his best.
I stumbled upon a movie called "The Doom Generation" several years back and was totally taken with it at the time. It's by Gregg Araki, who has made a lot of movies apparently but, despite digging TDG, I've only managed to watch one other of his films. That film was "Kaboom"---which, while quirky and interesting, I ultimately did not like. But I really liked "The Doom Generation" (but may have "outgrown it" by now).
"Doom Generation" reminded me a bit of "Repo Man"--which was also quirky...not really sure I'd recommend that though--or would I? Haven't seen it in years.
Horror movies--my fave is the original "The Haunting", which may seem dated and dull by today's audiences...but watch it alone, at night, with the lights off...and it still can be creepy! I also really dig things like "Suspiria" (someone else mentioned it), the little seen quirker "May", the original Brazilian Coffin Joe flicks "At Midnight I'll Take Your Soul"/"This Night I'll Possess Your Corpse" are primitive but fascinating for their time.
My go to unintentional camp favorites that i can watch over and over and over include things like "Peyton Place", "Valley of the Dolls", "Beyond the Valley of the Dolls", "Airport 75", "The Concorde: 79", "Earthquake" (Love my disaster movies), and "Beyond the Poseidon Adventure"...those are all very main stream, but all rather old so you may have NOT seen them. There are also two obscure Jayne Mansfield movies I love (for the wrong reasons). One is "The Wild Wild World of Jayne Mansfield" (made AFTER she died, yet "narrated" by Jayne--or someone pretending to be her--utilizing cutting room floor scraps, home movies, borrowed scenes from her lesser films and filler, filler, filler! It's a MESSterpiece--they made something from literally nothing. It gets bogged down in all of this nudie filler towards the end--but I find the film brilliant in it's own ripoff genius way) and "Dog Eat Dog" (kind of dull at the beginning--but once they get to the island with the Norma Desmond-like grand dame and her Max-like butler, the film explodes into this bizarre, unintentionally avant garde mess. Jayne runs around in a negligee and bad hair and almost seems like she's in a completely different movie. Cameron Mitchell gets blood on his face---and never wipes it off! Bizarre-o-rama wonderful!).
Intentionally campy/wanna be cult flicks you might consider: the 1989 remake/sequel "Dr. Caligari", the all-male comedy (men play all of the women and men) "Girls Will Be Girls" is pretty funny (like a warp, twisted modern "Valley of the Dolls" in Hollywood), "Shock Treatment" (the failed sequel to "Rocky Horror Picture Show") could be worth a look if you haven't seen it.
Some of the obscure moldy oldies out there ("Shanty Tramp", "Common Law Wife", "Another Day Another Man", "Monster At Camp Sunshine") that are unintentionally hilarious...stuff that Something Weird Video specializes in. Not all are classics--or even very good. Some are downright terrible--but some are just amazing gems.
There are probably dozens of things I could mention/recommend, but --of course---I just can NOT think right now. I'm probably way, WAY off of the mark---but that's the kind of stuff I dig.
Cha-cha-cha!
