Proven weapons, a most excellent selection.
I also personally stick to tried and true items. An M1A, 1911, 870 and a Marlin 925 round out my collection so far. I also consider the ammo as far as being a proven round. .308, .45, 12 guage and .22LR
Why I have each:
The 925 .22LR -
Honestly, if I had to head for the hills and I could only take one gun. It'd be the .22. Because in my 2 front pockets I can carry 1000rnds with no problem, it is light weight and reliable. I can take small game to live off of and it is still powerful enough with enough range to provide defense against 2 legged animals.
The 1911 .45ACP -
Talk about a proven design, it is nearly unchanged for 100 years. The .45ACP cartridge has a solid track record and the gun is extremely reliable. Oh and it is all metal. For a concealable firearm, it is hard to beat the 1911. Powerful, proven and it will stop a man. You can even hunt with it. I have it for home defense as well as CCW and open carry in the backcountry.
The M1A .308 NATO -
Yet another proven firearm. Though the Discovery channel special ranked it at #10, I found it amusing that all of the benefits that made the AK47 #1 were the same that the M14 had. Their issue was that it had the "shortest deployment life" of any battle rifle at ~4years? Of course, this is not accurate, because it never left service and is still in use today in Iraq. It provides accurate long range shots, it fires under almost any conditions, it is semi-auto with a detachable mag and is a battle rifle that will hold its own if we are ever have an alien invasion.
The 870 12 gauge -
In my opinion the 12 gauge shotgun is probably one of the most versatile weapons ever developed. Pump action allowing it to have an extremely reliable cycling action. It can fire buckshot, birdshot, bean bags, incidiary devices, sabots and slugs. You can use it for close quarters engagements like a home or building and you can take 50yard shots with just as much ease. Taking a target out to 100 yards with a smooth bore barrel is no problem with a modern rifled slug. The 12 guage proved its worth in the trench warfare of WWII and is still in use today in Iraq. I chose the 870 because of build quality and a proven record. I have mine loaded with buckshot and slugs nearby.
You have selected a fine assortment of firearms.