Rabbit Hole is a singleplayer mod settled in a surreal place. You start on the surface of the normal city and then get down to its undergrounds. And the deeper you get, the more weird things you discover. The mod is focused on massive combat and horror atmosphere. The gameplay is more quake-ish than classic half-life style, featuring massive zombie arenas and some experimental gameplay sections.
Today I played RabbitHole with oculus rift. It was a very interesting experience. Tho the mod needs some tweaks for full oculus support.
Coolio. Too bad I get so extremely motion sick with that damn piece of hardware. Might have to wait for final version of it^^
Hm I played hl2 with oculus the whole day and never had any motion sickness. But that's just me.