Event horizon is one of the few movies I actually find a bit frightening.

SOMA by frictional games.

It explores some of the usual questions about what exactly the human mind might be, if it ever becomes possible to scan, simulate, copy and transfer consciousness.

But it does so in video game form, in a way that makes you face those questions from a visceral, personal, first hand experience perspective.

It's a science fiction masterpiece.

You know what I love about Event Horizon?

That the evil hallway of spinning blades has a handrail.

Short Stories:

I have no mouth and I must scream - Harlan Ellison - this story was the apogee of sci-fi horror in the 70s and 80s.

We Can Remember It for You Wholesale - Philip K. Dick's original short story and the inspiration for Total Recall.

Weird French Shit:

Fantastic Planet - Animated french scifi about humans being kept as pets by giant blue aliens.

City of Lost Children - steampunk cybercultists

Classic Movies:

They Live - In case you're out of bubblegum

Tremors - broke into the wrong goddamn rec room, didn't ya?

Scanners - Pop!

Moon - really good psychological element and great acting.

Pandorum - fun (and a bit hammy) action horror romp.

Twelve Monkeys - really tight and suspenseful plot with great acting.

Being John Malcovich - not sure if this fits in, but a great mind-bender of a sci-fi movie.

I haven't seen anyone mention it but The Man From Earth is fantastic. It's literally just about a guy saying goodbye to his friends and telling an unbelievable story. There aren't any flashbacks or visuals illustrating the story. Just him talking and their reactions but it's so well written that it really draws you in.

Granted it's not horror but more people should see this gem

I don't have much of an idea on if it was small but the movie Sunshine (2007) comes to mind. Loved that movie. It's well worth a watch if you haven't seen it.

I've come to like Pandorum a lot over the years. I now make sure I watch it every once in a while.

I see no mention of Solaris

Very psychological movie

Pi (π)

Smart shut-in builds an implausibly powerful computer in an attempt to discern a pattern that is responsible for all things. He uses the golden spiral as evidence of such a pattern, and believes he will eventually take pi out to so many decimal places that such a pattern emerges there.

The psychological thriller aspect relates to what he experiences along the way, and how it ends. I have a theory about the ending, but no idea if it's an opinion shared by the creator or any others.

Triangle . The science fiction angle is that it's a time travel paradox. Predestination is another similar film, based off of Robert Heinlein's "--All You Zombies--".

Annihilation, if you can ignore the framing device.

Cube, though pretty well known, still fits 'small' IMHO, Given it's lows budget.

https://m.imdb.com/title/tt0123755/

Altered States comes to mind. It sort of straddles sci-fi and horror without really being firmly in either. Deals with some fringe psychology research during the 70’s going wrong in unexpected ways.

Brainstorm is more obviously sci-fi / speculative fiction… can’t say to much else without spoiling the surprises.

Neither one of these is going to seriously blow your mind, but there’s still food for thought. Bon appétit. 

Enemy Mine was pretty trippy. I saw it when I was a kid though so I'm not sure if it was any good or if it fits.

Vivarium was quite odd and different. I appreciated the original take on the age old concept of how alien and weird the suburbs are.

I'm not sure if it counts as smaller but The Thing, god damn, finally saw that one for the first time recently and it really is one of the GOATs.

Sphere from Micheal Crichton. Both the movie and the book are pretty good.

It is more sci-fi than anything else, but i think it fits the thriller category as well. Without going into spoilers, it is a story about scientists being deep down in the ocean, and strange things happening.

The first movie that came to mind is Aniara (2019). It's a great film that really goes beyond to show the hopelessness of being lost in space and how tiny we are in comparison. Fair warning though: This film will absolutely destroy you on an emotional level.

Is Andromeda Strain small enough? I love both the story and the movie. The combination of high stakes and routinously slow and boring procedures to scientifically-like contain\eradicate the unknown virus is hypnotyzing.

It is really campy and the books are much better than the movie but John Dies at the End is a fun movie that doesn't take it too seriously.

The French short film La Jetée is told almost entirely in still photos, but it's very haunting. 12 Monkeys was based on it. I like 12 Monkeys, but I actually like La Jetée more. There's also the short American film 12:01 PM which is excellent. Both are on YouTube.

Coherence

I love sci fi movies/books where not many humans are left. Even though not all are small stories: The day of the triffids; I am legend; 28 days; i love those because of the shots you see of cities without people, with overgrown buildings that are falling apart, animals thriving. I also like other sci fi stories, but the ones i mentioned above provide a temporary relief from all the news about wars, hunger, heartless people, news that is caused by greedy, evil people who seem willing to destroy the weak, other species, and even the entire planet.

I feel like Time Lapse isn't on enough people's radar. It's a tightly written sci-fi psychological thriller.

Cube

Existenz …one of Cronenberg’s most fun imho.

Prospect (2018, movie) - It steals all the cool you associate with crunchy sci-fi short-stories, and gets away with it. Beautiful, lovingly detailed interior sets. Sparse exposition, leaving your snatching at any little turn of phrase or namedrop wondering if it's world-building, or just how the characters talk. Just the right length. Respect for not making it Yet Another Miniseries (YAM (this is my acronym, you'll never see it again)).

Also wow, I haven't read any reviews until now, and I'm glad I hadn't. If you like sci-fi just watch it. It's 1 and a 1/2 hours long. I've already told you too much.

Event Horizon is my favorite horror movie.

I've mentioned it before, and I'll do so again! The Signal was a nice surprise, that sorta came and went in theaters, and we've watched it a handful of times since, as a spooky sci-fi comfort film. It's been a long while since the last time, though, so it may not have quite the same impact now, but that kinda makes me want to watch it more.

And not that it's at all smaller, but Shin Godzilla for another to watch over and over. So beautifully done.

I'm adding some great Spanish ones: Timecrimes, Shrews Nest, Rec, The Devil's Backbone

Oh, and a Swedish one: Let the right one in

Society (1989 film) has some amazing 80s body horror practical effects by Screaming Mad George (Joji Tani), who also worked on Predator and some of the Nightmare on Elm Street movies. And a general hatred of the rich, which is always nice.

For horror books, my favorite that I've read recently were The Twisted Ones and A House With Good Bones, both by T. Kingfisher.

Pi, Brainstorm, Moon, Primer.

Sputnik and Super Deep, two Russian sci fi movies I really enjoyed and were well made.

Europa Report and Life come to mind as well.

Not necessarily horror but Severance and Mr. Robot forever changed me. I’ve never been a TV person (except for Star Trek) so maybe those are bigger than you’re looking for.

Oh, and Alan Wake + Control. God, I love anything made my Remedy.