I read what someone said about Hurricaine Andrew and knew someone that was there. The power was out for weeks and there was limited security due to houses being torn open. A shotgun was a valuable tool!
I think that for a pure power blackout, without a torn apart home would not require a firearm (not a bad idea to have one) as much as it would require a way to provide some light, hygeine and a method to prepare and store food.
A good campstove with fuel a large ice chest and some non-perishable foods would be critical to have around. Water could be a problem too, depending on how widespread the blackout is. The pumps may be out. In that case a supply of bottled water or a water filter would be desireable. I have been in a large New England snowstorm that had power out for days and my main problems were keeping warm, eating and having fresh water. One plus to a snowstorm, there is plenty of water for the melting! Just have a stove, fuel and containiers available.
Hope some of these points are useful to some of you folks!