I've been known to refer to
Inside as the scariest movie I've ever seen, with the caveat that my viewing experience was very much enhanced by context. After finally giving it a rewatch a couple weeks back, the jury may be out, but I'm not retracting my statement. I can say for sure that it is insanely brutal.
Also, the soundtrack's great. Very subtle and minimal. Dark synths, serrated drones, pulsing rhythms, elegiac chamber pieces. There's an extended dialogue-free sequence near the end of the movie where a bunch of terrible things happen without any dialogue, and it's soundtracked entirely by a two-chord synth figure. It's sick as fuck. Go watch it if you can find it -- I torrented it.
Track listing:
1. Arctic Love
2. Memories, Part I, II, & III
3. Dark Beats
4. Discovery
4. Low/High
5. Memories (Redux)
6. Memories (Final)
7. Square Pads for an Eternal Dawn
More scary shit: