Radio transceiver, standard VHF marine when operating near inland shore, 121.5 MHz AM VHF guard channel capable aircraft band transceiver to contact rescuers and high overflying commercial and military aircraft visible by contrails, an optional amateur radio if a licensed radio amateur, (see Ham Radio) or an AM/FM/Weather/Shortwave radio receiver to receive precise time for celestial navigation as well as weather information
I'm not quite crazy enough to say that epinephrine will help you survive the inevitable zombie apocalypse (you can go here for that). I'm just suggesting in a roundabout way that if you happened to be in a situation where something was trying to eat you, the increased heart rate and blood flow to your muscles brought on by a well-timed dose might just save your life.

The problem with most of you prepper types is that you are way too early and wasting your energy. Yes of course I know what you’re all thinking is that we all must be prepared always and yes that is after all the whole point. But all things considered, past present and future .. technology is the real enemy and it has not yet fully evolved. Keep this date in mind and any years that are multiples of 9, (9-18-2027), have enough fuel to make it to the dessert, remove the battery and SIM cards from devices, bring dried food and chlorinated water water and dig in deep, good luck.

To me, the best option is to store emergency food. How much? If you have none, store enough for a few days. If you have enough for a few days, get enough for a week. How much you store depends on what time frame you think you're at risk for having to be completely independent. The early settlers of the southwest liked to store enough food for a whole year and still do to this day!