Sylvio [official site] is my favourite horror game of 2015. It's a quiet game, set in an abandoned park where the sky runs red, and you'll spend the majority of the playing time straining to hear voices in the static. Sylvio, you see, is a game about electric voice phenomena and its central scares are based around a tape deck, on which recordings made in the field can be played at various speeds, reversed and analysed. I've raved about the game at length and now there's a demo available for you to try.
There are no jump scares, just broken phrases that plant unnerving and distressing seeds in the old brain-soil, roots tickling their way down through the mind-dirt until they find a nerve. Then they tap into the nerve and by the end you're shaking your head at the screen as the pieces fall into place.
It's not a perfect game by any means. There's a single formula applied to each area: arrive, fend off apparitions, collect audio, analyse audio, solve puzzles, encounter [redacted], move on. It's a formula that works, even if some of the puzzles do detract from the mood by having the player character find bizarre and hazardous solutions to unlikely problems.
Sylvio succeeds because the developer understands how to unnerve without crossing over into shrieking and shock. Even the least credible elements of the plot are creepy because the delivery is almost always spot on.
The opening isn't the strongest part of the game - it takes a while to build momentum - but the demo should give you an idea of the feel, and help you to decide if you can tolerate the lo-fi graphics (used effectively, I reckon) and slightly floaty controls. The game is a cult classic in the making and, so far, hasn't found the audience it deserves. There are people out there who crave this kind of thing but might have been put off by the possibility of yet another Slender-style experience. Sylvio is something entirely different.