Personally, just combine Halo and Oblivion. (without the flood, of course.) I'm never happier with a gun in hand than when I am shooting things in beautiful, open, natural environments. Add some height, like in the AoTCR level, and cross the ruins with the Silent Cartographer.
But that's just me. I doubt that's anyone else's ideal FPS.
But that's just me. I doubt that's anyone else's ideal FPS.