+1 On SemperFiUSMC, he's spot on. Think passive defense first, then move on to active defense. Do all you can to eliminate the temptation from even entering their minds. I'd also add a possible Johnny Appleseed aproach to gorilla gardening and just go toss seeds all over the place as well, and...
BG380 - A few bucks more, but far easier on the hand, actual sights, and an aspect I prefer - unlike the LCP or SIG P238, when its got a round chanbered the hammer is not under tension. Although the long trigger on the LCP and the BG takes getting used to.
+1 for me on the Shotgun - Its the leatherman of guns, and in a SHTF it'd be indispensible for active defense. Not only can it shoot non-lethal warning shots of bean-bags or rubber rounds (only for the transistion time between normal life to accepted SHTF is here - IMO) followed by...