Much of my response is based on the area where I live; the southeastern U.S. Here winters are not normlly too strenuous, some water is normally available even in dry periods, and I am unlikely to be more than a few hours from a trailhead. When I used to live in the north, when I travel in more remote wilderness areas in the far north or west, or when I have any reason to expect difficult weather conditions, I would make some choices differently.
I think the classic ten essentials of mountaineering is a great place to start in any discussion of what to carry with you on a wilderness trek.
1) Matches. This includes any sort of items for producing a flame including matches, lighters, strikers, etc. Since they are generally so small and light, I usually bring both matches and lighters with me.
2) Fire Starter. This covers things like candle stubs, fatwood, steel wool, etc. Something to help get that reluctant fire started in tough conditions can literally be a life-saver.
3) Map. I know a lot of people who dont bother with maps in the more tame eastern backwoods, where trail are well blazed and routes often marked but all it takes is one wrong turn to get you totally lost without a map. It doesnt weigh much so bring it!
4) Compass. If you dont know how to read a compass, you should seriously re-think any decision to venture off the pavement. With a map and compass (and the knowledge of how to use them) you should be able find your own way out of anyplace you can walk into.
5) Flashlight, Like matches and lighers, I usually bring a couple. I always have one sturdy maglite or similar style of flashlight with a head band, and then throw a couple of the ultra-compact LED minilights in my pack for backup.
6) Extra Food. I never leave the trail head without a couple of granola bars at least. You dont really need food even for a couple days, but having it can be a real moral booster in a tight situation. It can become more important in northern or mountainous winter conditions, where you are burning a lot of calories just to stay warm.
7) Extra Clothing. In the summer for me this is a poncho (much more versatile than a rain suit, a hat and some gloves. In cooler weather, I include a gortex rain suit and polypropylene underwear. In the sort of winter weather I am likely to run into in the south were I live, this is plenty. When I still lived up north, I brought a lot more.
8) Sunglasses. This is certainly vital in mountaineering or on a snowy northern trip where snow blindness is a real hazard, but I think its not really essential in other areas. That said, I never leave home without at least one pair of sunglasses no matter where I am going.
9) First Aid Kit. Personally I think this should be a bit more comprehensive than the sort of first aid kits you are likely to find at most drug or sporting good stores. I like
Adventure Medical Kits myself and use them exclusively (I currently have one of their
Ultralight .7 first aid kits in my daypack), but there are some other alternatives including assembling one yourself with the help of a good wilderness first aid manual. Speaking of manuals, the training to use that first aid kit is as important as the kit itself. At the minimum I would sign up for a Red Cross first aid course. If you have the time and money, there are a number of wilderness groups that sponsor special wilderness first aid training for guides and travelers.
10) Pocket Knife. Most of us would probably place more emphasis on this than the Mountaineers do, but I think in the most eastern backwoods areas you can get buy just fine with a good folding knife. In the far north or western mountains I would want to have a bit more than just a pocket knife but even there this is acceptable as a minimum.
There
are I think two serious omissions in this list; water and shelter.
11) Water. At least one quart bottle of water (more in arid areas like the southeast). In addition I would also include some water purification tables or a water filter to get more.
12) Shelter. I have tried to address this to a limited extent by including a poncho in the extra clothing category. A poncho can be pressed into service as a temporary shelter, to at least protect you from rain and wind. If you have the room, or feel the need (such as in northern or high altitude environments), a simple bivouac shelter or small tent is even better.
I think after saying all that, I
strongly beileve in what
Aftertherain was trying to say (if I'm not putting words in your mouth?) that training and knowledge are more inportant than just about anything you can put in your pack. Read books. Take classes. Talk to people with real experience. All this will make you that much more "survival prone" than someone with a full pack but an empty head!
Always an interesting topic.