This is an idea that i came up with just moments ago.
Till Undeath Do Us Part is a romantic zombie survival game. The protagonist searches the world, fighting zombies as needed, to find his missing wife. This game has a few possible endings, mainly based on a few core missions. From those, side missions may be obtained, and those are not timed.
Zombies decompose, and some have guns, guns can be used and will not attract many zombies. Their intelligence decreases as they die, so you can out run them.