Adventure Medical Kits Outfitter First Aid Kit: A robust first-aid kit to have in a backcountry camp, the Outfitter is designed for trips of up to two weeks with up to 14 people. A detachable field trauma kit includes the essentials for a day--or unexpected night--away from camp. $120. (Buy here: Cabela's)
LifeStraw: The simplest water filter or purification device we've found. Simply dip the wider end in a stream, suck on the mouthpiece, and enjoy clean water that is free of bacteria and protozoa. $20. (Buy here: Green Beetle Gear)
Sunglasses: These are especially handy for preventing snow blindness.
Firesteel: You can never have too many fire-starting devices.
Large trash bag: See no. 12.
Square of foil: As with the trash bag, the number of uses for a square of foil is limited only by your imagination.
Hand sanitizer: The alcohol-based stuff makes a great firestarter. Also useful for sanitizing hands.
Fixed-blade knife and 550 paracord
Drink mixes: Stay hydrated, alert, and energized with Wilderness Athlete powder mixes. A few envelopes will add very little weight to your kit. Bring along a stainless steel water bottle to drink it from. $30 for 20. (Buy here: Winded Bowhunter)
Survival fishing kit: A few feet of monofilament, some hooks, and split shot in an old pill bottle is a good minimalist approach. If you can't be troubled to round up this stuff on your own, Best Glide sells a more thorough kit for about $8. (Buy here: Best Glide)
Extra pairs of wool socks
Paperback novel: If you're going to be stuck for a while, you'll need something to take your mind off your plight.
West Marine Coast First Aid Kit: The waterproof case contains your standard first-aid materials, plus marine-applicable stuff like motion-sickness tablets and burn cream. $11.