Since you're plan is to use it for a natural disaster, zombie, marshal law, bug out type situation... I'll go ahead and say it... GET AN AK VARIANT!
All kidding aside, I would suggest something with a barrel length under 20" and any reliability features you deem worthwhile. The flat-top models are way more versatile than the ones with built in carry handles. You can put one on a flat-top model too. If you want the most basic sights try the Magpul MBUS or Troy BUIS flip-up sights on there.