There are many lists but this is mine. They are arranged in a relative order of importance and would allow one to survive overnight if necessary (imagine that you have broken your leg, can’t be rescued that day, and have to spend the night outside – what would you need to survive in relative comfort?). That should determine the essence of any list.
1. Water. It is hard to survive without a water source. One can go several days without eating.
2. Signalling mirror/Emergency Locator Beacon. A mirror is the best simple way to signal help as it can be seen from a long distance especially from the air. Whistles are of less use as sound does not travel well. Emergency locator beacons are obviously the best things to have if help is needed. One of the best is the De Lorme Inreach, a 2 way satellite communicator with 2 way texting for SOS and personal communication. It sends up to three pre-loaded messages, SOS in emergencies, and has automatic location tracking every 10 minutes. When coupled with the De Lorme Earthmate PN-60W GPS, it allows outbound and inbound messages with it’s internal keyboard and message screen. This also has De Lorme Topo maps for all of North America. Cell phones, UHF Radios, walkie talkies and satellite phones (very heavy and thus impractical) have value depending on location. Lighting a safe fire is useful 24 hours a day.
3. Large garbage bag. A large orange leaf bag can serve as an emergency shelter and increase visibility. A bivy sack may be a better option but is much heavier. The Integral Designs 8’x10’ Siltarp 2 is another light great choice.
4. Warm clothing. The amount varies with the season but every pack should have a warm jacket (down is light and warm but shouldn’t get wet), rain jacket and pants, long underwear, touque, gloves, and neck warmer. A light sleeping bag would be nice (the Western Mountaineering Ultralite weighs less than one pound).
5. Seat cushion. Keeps your bottom warm and off the ground. Thermarest seats are best but closed cell foam pads also work well.
6. Map and compass. If your GPS fails (batteries run out), a compass is invaluable. It is worthless if the declination is not known. 1:50,000 topographical maps should be carried on every hike.
7. Fire. Fire starter, matches, lighter
8. Food. Ideally should carry an extra day’s food, 1000 extra calories over and above that days food would be a minimum.
9. First Aid Kit. Athletic tape, pain killers and steristrips with bandaids would be a minimum.
10. Insect Repellent. DEET is safe and the best consistently effective repellent.
11. Flashlight. LED headlamp best. Spare batteries. A must if you have to walk in the dark which is not unusual.
12. Knife. Multipurpose tool like a Leatherman with pliers may be better than a Swiss Army Knife but are very heavy and may not have many actual uses (cutting off arm if trapped by a rock). Keep blade sharp.
13. Sun protection. Sunglasses, sunscreen and lip protector with sunscreen.
14. Nylon cord. Useful for many things.
15. Keys and Identification.
16. Pack. One large enough to hold all this stuff. I like the 38 liter Deuter Futura.
17. Common Sense.