Not going to discuss the game design until we've built prototypes, but we're definitely working on my first-person physics game. We found a very interesting angle in terms of the story; it's a bunch of "freedom fighters" (sort of, I'm trying to be a little secretive) vs. a Government agency (sort of), and you're right in the middle of it.
Tomorrow is a big day; I'm presenting my story treatment, gameplay proposal and also marking the various (now outdated) concept art pieces our art guys have been working on. If all goes well, we should even have a basic level design down on paper by the end of the meeting.
The great things about this assessment is that it's been an excuse for me to study nuclear/quantum physics. Our game will obviously be using faked/hollywood/fictional physics, but it's nice to take some interesting concepts away and use them to drive the story into fun places.
EDIT: To clarify, about 2 weeks ago we all had the final vote on the game we were going with, and we decided on the physics game (much to the annoyance of the animator who came up with the school idea). Since then, my friend and I have gone through about 3 different iterations of the high-level mechanic design, and many, many more iterations of the story. I think we both are finally happy with where the game is going now.
