If you're looking for a .22lr rifle that breaks down the AR-7 fits the bill nicley. I think the rifle is now sold by Henry Firearms. The barrel unscrews from the action, and both pieces fit into the stock. The whole thing will float if dropped into the water, another plus from a survival stance. If however you don't need it to break down Taurus Firearms makes a nifty .22 pump action rifle like they used to have in the carnival shooting galleries many years ago. Pump action and either bolt or lever action guns may serve you better if you plan on taking them out in the cold of winter. Less likely to have the action gum up because of lubricants freezing.
As far as a 12gauge shotgun goes, either a remmington 870 or mossberg 500 is what I would recommend (both pump action). I own a mossberg 590 (cause I'm a tacticool idiot at times) and a maverick 88 (mossberg 500 clone) with a pistol grip.

-Bill Liptak