It was called "Airlock" and it was set after some mysterious event happened that sucked all the air away from the planet and killed pretty much everything but you and one other person in a bunker like yours with their own oxygen supplies. Since the world outside the bunker would be rendered sterile, the billions of corpses would be well preserved, save for dessication, all just laying where they dropped when the event happened. You'd be playing as one of the two survivors and would talk with the other over a radio, when one day they'd stop responding. With nothing else to do, you put on your airtight suit, grab your gun and leave your bunker to go see what's wrong since they were your only friend.

You'd be practically deaf when outside the bunker because there'd be very little, if anything, for sound to travel through, so you'd only be hearing the sound of your own breathing inside the suit and the beeping of an oxygen gauge that ticked down over time, getting louder and more urgent after passing certain oxygen levels.

You wouldn't be alone, though, because somehow, some things, maybe the things responsible for the apocalypse in the first place, or maybe just their pets, would be out there. They wouldn't need air, and they'd be deadly silent predators. You could only be aware of them through visual confirmation, and they'd be these haunting, stalking creatures that could get to you anytime and anywhere outside your bunker, and they could get you at a moments notice since you wouldn't hear them approaching.