Whenever I embark on an expedition I'm faced with my own conflicting desires for a blade small enough to hurl end-over-end at trees and large enough to wave through the air with a satisfying swish swish. But, as the good people at Survival Topics note, "Choosing the right survival knife is more than an exercise in individuality--your very life may hinge upon its proper selection."
In general, I suggest a full tang, drop point blade approximately six-inches long that has been tested to cut through airplanes and oil drums (knife manufacturers presumably test on these items because of the large number of consumers who slice their way into and out of airplanes and oil drums each year.) The Becker BK10 is a good example. Fallkniven also makes an excellent model. But, ultimately, the choice is yours. Your knife should make you happy and confident, whether you're wandering the aisles of your local grocery store, secure in the knowledge that you could slice that can of chili clean in half, or if you're stranded in the wild, a storm brewing, surveying the carcass of a moose for an entry point.