In a less brutal survival situation I'd go with a Springfield M6 Scout.
Over and under gun...nice. Though the calibers of both barrels are a bit light for me.
Personally, I'd probably take a Saiga 20 Gauge shotgun with traditional shot ammunition and slugs instead. Of course, that probably doesn't have the same range as a 22, but I'm not expecting any zombies to get the drop on me first with a gun...