Except for American Guns, I enjoy all of them, to one extent or another.
Some random thoughts:
Sons of Guns: It feels less upbeat, more choppy and scripted this season than the last two. I'll still watch it, but I'm less enthused...BTW, the "autocannon guy" is from Pennsylvania, and appeared on a Current.TV segment about Knob Creek.
Alaska Gold Rush: I give them kudos for "arming up" out there, but during season 1 episode 1 they depicted the "buying spree" of provisions, and it seemed like they bought far more guns and ammo than they could possibly need (I'm not in favor of ownership limits, just seemed like they could have been more frugal, given their tight financial situation). In addition, I don't think they drove the weapons through Canada (at least not the handguns) - there was a cursory scene mentioning the weapons going into containers to be loaded up on the ferry, which bypasses the Canadian import issues altogether.
Doomsday Shows: I think they're fun to watch, and I say, "meh" to the whole "violating opsec" aspect of showing the bunkers on TV. The locations are generic enough (I think) - In a really bad situation, a lot of people that may have watched these shows will be dead or incapacitated. "Hey honey, where was that cool bunker with enough stuff to feed all six of us? Oh, that's right - I can't watch the repeats, cable and power are down." I think most people will be too preoccupied/scared to go on anything more than a short journey to look for one of these bunkers. If they're well hidden they may not even be found. And if they are, they look quite defensible.
My biggest issue is how are people going to get to their doomsday shelters - take that one fellow who lives on the Florida coast, but has a shelter up in the Georgia mountains. He's mostly concerned about Tsunamis, which probably have the shortest warning buffer of just about any large-scale disaster.