Sorry guys but looks like I have to be the one to say it since no one else has. Accidental discharges are negligent discharges. The firearm discharged because a finger was in the triggerguard when loaded and not shooting, thats not an accident thats negligence IMHO. Ignoring safety isnt an accident, its negligence!
SHTF battery... I'd suggest:
1. on-you-at-all-times centerfire handgun
2. scoped centerfire hunter/sniper rifle
3. intermediate centerfire rifle/carbine for runnin & gunnin at various ranges, preferably semi auto with large capacity
4. semi or pump shotgun(preferably 12 gauge).
Keep in mind that your handgun and/or intermediate rifle picks can double as a .22 rimfire if you choose a platform that has .22 conversion kits available, so theres no need for a dedicated .22, if for whatever reasons you need to leave some weight/guns behind(sic!).
All you need to do is insert your favorite guns into the list.
Of course it goes without saying(even though Im saying it) you need to be proficient with each arm if you expect them to save your life, not just one time but many times over. Dont forget to think about the interchanging of trigger/action styles. Going from your #1 DAO pistol to your #2 or #3 1-2stage triggered rifle might screw with you just when you dont need to be screwed with.
My personal picks(favorites) are:
1. ANY good quality 1911 and/or Kahr K,T,P,CW (I dont have much experience shooting Glocks, but they just dont feel right in my hands)
2. Scoped M1A - .308win
3. AK47 - 7.62x39mm + red dot
4. Saiga 12 - 12ga
All are loaded via detachable magazine and can accept large capacity magazines, whether needed or not. And all are accurate enough to get the job done and make me feel safe. I own all and others except the M1A which is on my wish list, my granddads 30-06 takes its place for now.
Notice I picked two single stack semiauto pistols, THATS NOT ADVICE, thats my own preference for grip size, trigger feel and portability. I have funny hands and they dont like the feel of most handguns. Actually im IN LOVE with Kahrs nowadays I cant help it, I just like them side to side, front to back, top to bottom.
78corvette said "Bugging in vs bugging out... either way its going to suck." Those are words we should not forget. Cheers.