1. Ruger AR-556 (with assorted uppers for diff cals)
2. Colt .45 cal 1911 (X2)
3. Tactical 12 ga

I'd add #4 equally important to the above list:

The ability to do your own reloads & a little chemistry knowledge (like knowing how to make smokeless powder in a post-apocalyptic pinch). I have an old school cast iron Herters Super Model 6 press rig w/all the acoutrements. It's not very popular (nor easy to find at gun shows) cuz everyone wants new & shiny, but finding dies is easy peazy (they are everywhere at shows). You know it's old when it's coating is baked-on enamel, but I dig the 50s-60s look (and old or not, it's built better than the newer stuff).