This has definitely been an interesting thread to look through and given me better ideas on how to manage what I use (the EMS field guide is something I need to get!).
I've been keeping not only a bug out bag, but also a quick reaction disaster bag as we live in tornado alley. This is for times when disaster is localized and basic services are still online, just not in the immediate area. IMO, this is a practical application and relies less on defense (although that is included) and more on continuity. This bag goes with me any time we head for cover during a tornado warning. Probably the most crucial components are medical and comms. There's been several documented cases of people being buried alive who could have been rescued sooner if they'd had a cell phone/radio of some sort. I aint goin out like that!
Water (including purifiers)
Medical (mostly focused on cuts, burns, fractures, pain killers, scissors)
Light (flash light, cave light, chem lights)
Food (basics that keep you going)
Comms (Yaesu VX-5Rs which can do HAM and FRS (Good for monitoring RACES/ARES and does not rely on cell towers), back up cell phone)
Solar charger (strong enough to charge all the electronics in the bag)
Marker, pen, wax pen, water proof note pad
Firearm (one in the bag, although I usually pair the bag with a shotgun as well, time permitting when on alert for bad weather) and ammunition.
Spyderco blade
Leatherman