Personally, this is the one I'm most excited about. Implementing the Rift is going to be a challenge that I look forward to seeing unfold. That GIF up there was recorded with the movement of my very own neck and head, and I've gotta say, it's quite an intriguing experience being in the control room.
While it's great to be transported off into magical lands and warzones in the Oculus Rift, often, the lack of wind against your face, bullets hitting your stomach or fact the simple fact you're sitting down holding a controller that keeps grounding you back in reality. I tried this in the Opposable Games office, which seems to mirror the control room effectively enough as far as tactile sensations go, and it was really effective. While there are solutions to many of these problems coming to the market soon, it's hard to say how affordable they'll be and how well they'll do commercially. We want as many people as possible to play this game and have tons of fun doing so.