I've read many fine suggestions in this thread, so I'll just mention a few things that were not mentioned: A water filter bottle and/or straw. My research makes Seychelles my choice in both catagories. YMMV; A 4-way silcock key to open and close commercial water hose outlets (Ironraven, how could you forget? I learned this from you.); 3-4 flashlights- A Photon type button cell or 2, a small headlamp with xtra batteries ( e.g. Princetontec Scout), One or both AA/AAA flsahlight ( e.g. Zebralight SC-51 with headband and Fenix EO-1). Why 4 lights? Battery variety , backup, handsfree & share with a fellow. If regulations permit, a Boker Cop Tool; and a good trauma kit with the basic knowledge to use it, even if its only from old Army/Marine training videos on U-Tube. Such a kit might include 1-2 Izzy bandages (the 2 pad model is best), TK-4 tourniquet, primed compreesed gauze, chest seal bandage, 28 Fr. nasal airway, Celox or Quik-clot pad or Combat Gauze & small sharpie (mark the head if you use hemostatic dressing). Sounds more complicated to use than it is.