This is my stab (pun intended) at the horror-movies-you've-never-seen list. There are lots of these types of lists out there, and I'm sure someone will read mine and think that these aren't obscure at all so, oh well. But I'd like to think there are several horror movie fans who won't have seen at least some of these.
Start your marathon with just the first twenty-five minutes of When a Stranger Calls Back from 1993. You don't need to watch the rest of it, but the opening sequence is tense and terrifying.
For the first full film, watch Kill List, but only if you've got a strong stomach. It's not a gorefest exactly, but the violence that's in it is pretty brutal. But, more than anything, this film about two hitmen getting in over their heads is one evil ride.
Now take a little bit of a break with Dead of Night, an anthology film from the Ealing Studios in 1945. Definitely scary, but some of the stories have a pretty light touch. The ending, however, is probably my favorite sequence in a horror film ever.
Triangle is a little-seen thriller from 2009 that stars Melissa George as a single mother trapped in a bizarre time loop on an abandoned ship. If you remotely like these kind of mind-bender films, then you'll love this, and it's scary to boot.
And finish up with the highly entertaining 1980s thriller Psycho II. It shouldn't be good, and of course it doesn't come close to the original Psycho, but it's a fun, gory twisty horror movie. (I will admit that I haven't seen this one in a while, but I remember it fondly).
Happy October (the month of scary movies)!!