I have been trying to find the perfect field knife for more than forty years. For the most part, I mostly succeeded as a collector, because I've kept every knife I've had. Over that time my knives have been folders and fixed blades made by Buck, Kershaw, CRKT, Kabar, Victorinox, Ontario, Camillus, Spyderco, Bark River, Zero Tolerance, Martindale, Becker, RAT, Swamp Rat, Frost's of Sweden and more than I can even remember. I have never found a single knife that is good for everything one may need or encounter. However, if I was forced to pick just one knife to take into the bush or for survival, I would pick the Bark River Canadian Special. It's about 9" long with a 0.17" x 4" full tang blade of A2 steel. It comes in a leather sheath that molds to the blade and covers the knife up to about 1" from the end of the handle. Out of the box, it's by far the sharpest I've ever seen. I paid about $125 for mine. I'd use it for everything except digging. It would not do anywhere near as well as a machete for clearing brush or chopping trees, but it would come nearer to being good for that than a machete would be for slicing meat for cooking. The Bark River knives are not cheap, though. If you feel the need for a big knife, look at the Cheaper Than Dirt DBA models. KnifeTest.com did a test on it - http://www.knifetests.com/CheaperThanDirtRoughUseKnifeDtest.html. $10 plus shipping. Should give you plenty of money left for a smaller blade such as Swiss
Army or nice mulitool so you have all bases covered.