What I typically carry in my 'week' pack. In a pinch it'll stretch to a week if you really need to, but it really isn't all that heavy.
1) A good fixed blade knife of around 4-6 inches. I've got bowie type I carry.
2) Lots of strike anywhere matches in a waterproof container. 20-30 of the wood stick type in an old plastic perscription container. Seal it up with some rv sealant and you don't ever haver to worry about water getting in. While your at it, stuff several cotton balls, or a bit wad of lint off of your dryers screen in there (dryer lint lights and burns like it was soaked in gasoline, hot, fast and bright).
3) Two of those 'emergency' blankets. They keep you pretty warm if you have curl up somewhere, and with two you can make a decent shelter if you have to. Plus they double as signal mirrors if you need one.
4) 50 foot of parachute cord.
5) A compass, and a good one. Along with a map of the area I'm gonna be in.
6) A good canteen (preferrably a metal WWII type with the cup that goes around the outside). With a metal canteen you can boil water in the canteen and the cup at the same time.
7) 14 of the powerbar energy bars. I don't like them but if I have to I can get by a week on 2 a day without feeling too bad (at 230 calories apiece).
8) A multitool with a good 3-4 inch saw.
9) Socks and thermasilk underwear.
10) Lightweight raingear. Pants/top I use Guide Series Tech 2.5 right now. Its dry, cuts the wind to nothing, and when stuffed with pine needles makes decent winter insulation.
11) Water purification tablets.
12) Some duct tape.
13) First aid kit (a good one with several needles, safety pins and a full thingy of dental floss. Need be dental floss makes decent sew yourself up thread.)
14) Rescue whistle.
15) One of those LED shake up flashlights. No batteries to go dead, and it keeps you warm *grin*.
16) A couple small candles.
Most of everything gets double wrapped inside of quart freezer bags. If I need them, they're still water proof, plus it keeps everything inside dry.
That's the basics. Weighs 4-5 pounds with the canteen full.
Most of the time I throw in a half dozen or so chemical hand warmers, and a Katadyn pocket water filter (which is worth its weight in gold in a survival situation). There's most likely a couple trioxyne fuel tablets, and a hatchet in there someplace. Considering I usually hunt with a blackpowder muzzleloader, I've got a good supply of either percussion caps in a waterproof container, or a good supply of flints, alont with a half pound or so of powder. I also typically carry one of those fire pistons. Oh, and a plastic sealable shaker of salt. Makes everything taste better.
After a while it typically gets a bit heavy, and I keep thinking I'm possibly going to pare it down, but I keep adding more items to it as time goes on.