It's the buildup that gets you
I've been daydreaming about the possibilities of survival horror games that use the Oculus Rift to further draw players into the experience, but this title, Alone, goes in a completely different direction than what I had pictured. Essentially, you're playing a horror game within a game -- and it starts to bleed into your character's reality.
This video by Tyler Hodder of the VR Brotherhood does a tremendous job of walking through why that premise is so unsettling. I've heard colleagues who have tried the Rift talk about how wearing the headset and closing yourself off from reality leads to paranoia about your real-world surroundings; Alone builds on that concept in what looks to be an effective way.
As an experimental project, this is super interesting, but I'm not sure if it's enough to build an entire game out of without the scares becoming predictable. That's far from a unique problem, though.