@david thats definately a difficult question to answer, mainly because it has so many answers, it depends on experience knowledge, familiarity, personal preference, expected time to spend away from civilisation, and many other things.
personally i would say the ABSOLUTE minimum is a large amount of knowledge and a good knife between 6-10 inch blade, about 3/16 inch thick, FULL TANG...not a stupid hollow handle thing, or some crap with a compass in the hilt, the choice between stainless and high carbon is upto you, stainless is more moisture and rust resistant whereas high carbon keeps an edge longer and better (the debate between the 2 is ongoing and there is no definitive answer, its down to you to decide).........so as you can see just choosing a knife is hard, which is why i recommend learning as much as you can, and going out into the garden and practising!! reading how to make a fire bow is useless without trying it in real life, once you got some experience trying out these techniques with some different knives will help you find what you like best
....a cheap knife is easy to come by, there are enough things you can buy for under 50 quid that are good quality and myriad in design, i recommend heinnie.com myself
anyway james had some great points of things to put in
.....a good thing to remember is " one is none and two is one"...make sure you have more than 1 way of purifying water, making shelter, making fire and getting food. cover all your basic needs several times before trying to get things to make life nice, survival is first and foremost.
i dont think any of us have a bunker btw....yet