As I mentioned the other day, looters are a concern any time there's any kind of civil disturbance. I've seen a few news reports mentioning that looters have indeed crawled out from under their rocks in the wake of the southern California fires. (Example.)
Looters are scavengers, creatures of opportunities. While an AR-15, AK-47, or Mossberg 590 is a fine choice for dissuading them, you don't need a "tactical" gun. An old .30-30 or a cheap Remington 870 Express will provide plenty of firepower. The key is the knowledge of how and when to use it, and the will to do so.