One concept I've always been enamored with but rarely see even attempted is "playing as the monster". I've heard Demon Souls has a degree of this, but I don't mean as a feature, nor as what it usually turns out to be when a game attempts it, i.e. "playing in a monster suit". Where you could be playing any random game with that gameplay as a human character and no one would notice. As an example of what I'm thinking, look at, say, Left 4 Dead. I'd put it in the early days of the zombie apocalypse; not abandoned, but hundreds of panicked people running through the streets, groups barricaded into buildings, paranoid and armed survivors prowling for supplies. Pre/mid-collapse. You'd play as a sort of enhanced version of the special infected, not invincible, but not made to evaporate under a half second of gunfire.
It wouldn't be a "race" game like L4D, but a slow-paced hunt, possibly in a sandbox or at least very open-area setting, like Thief games. You'd use various senses like smell and hearing to track humans, moving slowly through an alley at night, and hear a whisper from a window that gives away the location of survivors. Use scare tactics to separate and pick them off, summon and control regular zombies to siege their safehouses, climb walls and break windows to find ways in that they didn't think to barricade. It doesn't necessarily need to be zombies, but any "predator" standpoint, where I can swim across the bottom of a river and drag people off boats. A monster movie from the monster's view, a variation on stealth games with its own twist to gameplay and goals.
