if you really want to be prepared with firearms and ammo just in case - here is my advice -
keep it simple - i really like Glocks - but for longevity and ease of repair, the more simple the weapon the better. so for pistols, revolvers will last and last and last. for rifles - my advice again would be think simple bolt action hunting rifles - again, i like my M1 but could probably fix the K98 easier than the M1.
rather than stock-piling ammo, get a quality reloader with all dies (and back-ups) - invest in some lead dies for bullet making and stockpile powder and primers (the hardest things to make yourself) instead of buying ammo - roll your own instead