I have a number of guns in my collection that I acquired for various reasons. Some I acquired because they had historical interest to me, others because they were inexpensive recreational shooters, and others, such as my cowboy guns, for informal cowboy action shooting. Some for no reason other than they were "cool." Recreation aside, there are certain guns I'd recommend for anyone wanting to put together a basic survival/end of the world arsenal. The hard part is establishing their priority. For years I played the mental game of "If you could have 10 guns, what would they be and why." Then reduce the quantity one by one until left with "if you could have only one gun, what would it be?"
I see the quest for a minimum battery of guns to be similar to knives. There simply isn't one gun that does everything, any more than there is one knife that chop down a tree, peel carrots, and conduct surgery. So while there is no one gun, there are categories of function, and for this I've narrowed it down to 5.
I have listed the guns I would pick in each category. There are many quality guns. I have made my selection in bold within each category taking into account all the reasons above. As time permits, I will expand on my reasoning.