Here's one that's notable for a reason you may not expect: THE LAST WOMAN ON EARTH (1960), directed by Roger Corman.
Basically it's about a wealthy businessman, his hot wife and their lawyer who end up being the only survivors of some mystery plague that's wiped out the rest of humanity (although it's not like they really leave the area, so possibly only Puerto Rico was affected). Now, from the title and the lurid DVD cover, you might expect this to degenerate into an obvious plot where the two men duke it out over THE LAST WOMAN ON EARTH! You'd be partially right, except for one thing:
You didn't count on Robert Towne writing the screenplay AND starring as the hapless lawyer friend. Towne, who won an Academy Award for Chinatown, wrote and starred in THE LAST WOMAN ON EARTH!
So basically you end up with a really cheesy, low-budget effort with all the hallmarks of your average B-movie, with the exception of the screenplay, which really confused me for the duration of the film until I discovered who the writer was. I can't say it's comparable to Chinatown, but it's definitely worth watching just for the strangeness of watching the script straining to overcome its puny confinements.
ALSO RECCOMENDED:
-ZARDOZ, in which Sean Connery wears a red diaper and must defeat giant flying stone heads that spit guns and lines like "The penis is evil!" Then he goes after a race of immortals who want him to teach them about sex. Then he runs around a hall of mirrors screaming "Kill the tabernacle!" An art film that nearly cost me a number of friendships after I screened it at my house.
-MARS NEEDS WOMAN, in which Martians need to repopulate their planet by kidnapping human females while saying things like "The exotic dancer is secured!" Notable for starring a former Disney child star who was later kicked out for charges of homosexuality.
-ELECTRIC DRAGON 80,000 VOLTS: Not actually a bad movie, I just love the title so much. It's a Japanese film about a man who communicates with lizards and must control his ability to generate massive amounts of electricity by playing his guitar really spazztically. Then he is challenged to a fight by the Electric Buddha. ....Yeah. You should watch it.
Ya gotta tell everyone, Hatcher! Soylent green is PEOPLE!!