End of the world senarios are always an interesting discussion.. honestly it would really depend on what situation.. If I could stay out in the country where I am currently near my house an acreage around me.. well, my HOFSH on my pack, an active duty on my belt and a SFNO on my LBE my benchmade mini rukus... along with my DSA FN Fal para. for punching through trees and heavy brush
If I had to go into urban areas for scouraging, I would want my ASH1 for prying into windows and such along with my leatherman tool for working on mechanical things.. and my hellrazor as a fighter.. I would be mobile and needing more of an ammo supply, thus my M4 with ACog TA31 on it with 12 mags would be the ticket.
If I'm way out into the boonies getting away from everything and having to make my own shelter, I would go with the FFBM on my pack, maybe my Sfno on my side and again, the fal for woodland penetration and range...
usually when I just go to the farm or am out messing around, I've got my BATAC on my or recently my favorite is a skinny Ash..
What ever the situation... Busse definately has a piece to fill it... and between DSA FNs, and my Bushy ARs, all the bills are filled... Oh ,forgot my Glock 22 tactical with ghost ring sights.. Should fit most of the sitations..
Some good reading: Chuck taylors: the fighting rifle, Life after doomsday, by Bruce Clayton, The Ultimate Sniper, by Maj. John Plaster and some good old MOUT TM/FM manuals..