Its occurred to me that perhaps my last couple of answers to scenarios might have sounded a bit sarcastic. I am actually trying to make an important point (at least, I think its important). Survival is about living to the next day.

We carry all these gadgets with us because we don't actually know what emergency we will confront on any given day. But your brain is always your best survival tool.

IF you know beforehand that you're going to possibly be stranded on a desert island, make sure you have a GPS and a Satelite Phone. Then you can leave on short order!

And IF you know beforehand that you've got 5 days in the desert (and only 5 days), nothing is going to be more precious to you than water. You can make it 5 days without eating, certain religious types do that kind of thing as regular ceremony.

So why do you need a fire? To cook food, to boil water? If you're really looking at -40 degrees for a brief time before sunrise, burrow underground! The desert ground stays at a near constant 58-68 depending on where you are.

Why do you need a knife on a five day walk? To build a shelter. Why build a permanent shelter if you're walking? To hunt game?

Bleach to purify water? Not if you bring you own water with you!

I still say the correct answer is as much water as you can carry and maybe some cordage to help distribute it arround your shoulders.

If you just wanna have a 5 day walkabout that's fine, take all the gizmos with you and put 'em in you're $100 pack. But that doesn't really speak to the question at hand.