I really don't want a 50 lb pack as my Get Home bag, so I choose a lot of items that can serve more than one purpose. Sometimes, it is a primary purpose. Other times, the item can double as redundancy for another basic survival item in the bag or complement it to create a luxury. A few of my favorites are listed below. I'm not listing the obvious items everyone carries, like a knife, fire-starter or water bottle. What are your favorite multi-purpose items?
1. Dental floss: It tends to be very strong. In addition to its obvious use, it can be used for sewing thread (ensure you have a needle that has a big enough eye), suture thread in a pinch, substitute for twine, making a crude shelter by tying corners of mylar blankets or tarps to spots or trees. I carry 4 X 10 yard mini-containers with cutters.
2. Small bottle of 91% isopropyl alcohol: I use a 2 ounce plastic dropper bottle from REI (test in store to be sure no air escapes when you squeeze it) useful for sterilizing stuff, a solvent, ear drops to prevent fungal infection after swimming, drying tinder and helping start a fire, cleaning skin around a wound. The 70% isopropyl (rubbing alcohol) isn't as useful as the 91%, especially for sterilization. These are usually side-by-side on the store shelves.
3. Mylar blankets: In addition to other lightweight bedding and a heavy duty mylar tarp/blanket, I keep at least 3 of the small cheap ones in each bag for so many uses. Many articles have been written about these because they have so many uses such as a poncho, groundcloth, rainfly, sling, fire-reflector, foot-warmers and water proofers (before getting feet into cold water), etc..
4. Metal cup: whether a canteen cup or deep stainless cup (not those skimpy Sierra cups) these can be a major kitchen-creator. Use to boil water, mix food, scoop water from sources, catch rainwater to fill your bigger bottles, store a roll of TP in your pack to keep it dry and round, hold a tea light for fire-safety. Depending on which bag, mine is either a GI canteen cup with stove stand or a round cross-section 28 ounce cup which holds a roll of TP perfectly. VERY WORST CASE you can soak the TP (in the metal cup) with the alcohol and light it to keep from freezing to death (this is the luxury item mentioned above -- a chemical stove). This is a very hot fire, so do it in a place where you can maximize saving the heat (small rock, earth or snow shelter) and keep safe from fire or melting something.
5. Tea Lights: in small metal/foil cups, the 100 for $8 or less kind, unscented. First use is to prolong the life of your other fire-starters. Use 1 match to light the little candle and use the candle to light your splinters, tinder or alcohol dotted square of TP to start your fire. Heat source : in your metal cup in a small space made of your mylar blankets, you can actually warm hands, feet etc.. Heat water: half a canteen cup of water over a canteen-cup stove with a good tea light or two can give you a smokeless unscented fire for hot water in a short time. If accomplished in your mylar hooch, it will also warm the space somewhat. I keep at least one empty plastic medicine bottle full of these in each of my 'bags.'
What are your multi-purpose favorites?