I agree with most of the commentary here. A person in decent physical fitness or slightly overweight should be able to carry their main equipment with backups on the knives, fire, lighting and emergency shelter side.

If weight is truly that much of a concern (say military or flight or just packing a lot of other gear), then go with lighter equipment... usually pricier, but well worth the cost in those situations. Titanium, Aluminum, bakelite type plastics and lightweight ripstop nylon all come to mind.

So, make sure you have a couple knives, with one of those being a multitool. Best situation is Multi, Fixed, and a backup folder. Carry a primary high throw hand held, a Photon, and a headlamp all with extra batteries. Maybe toss in an extra photon. Waterproof matches, mini-lighter, ferro-rod, and maybe backups of each wouldn't be a bad idea along with Tinder. Poncho, trash bag, emergency shelter or bivvy (all x2). In addition, I don't see folks mention it, but I would at the least add in a simple metal reflector in addition to your plastic/glass mirror for signaling. Super-light and easy to pack.

I would recommend spreading that gear out so you reduce your chances of losing or ruining items. You can carry triple redundancy of all of the above, Knife, Light, Fire, Shelter, signal, for in the 5-10 pound range without trying too hard. Spread it around in pockets and packs and you'll hardly notice it.

I've started to think that carrying extra water is really what you should do... get your gear to where you like it and then fill up on water. Overload the water. Worst case, you can use it up or share or even dump some if weight becomes a concern. And don't forget your ETS PSP and some Duct Tape!