As others have pointed out, actually having it when you need it makes a difference, the best handmade knife in the world don't mean squat if you don't have it when you need it, and you never "plan" on being in a surival situation.
So saying if you are going out camping or even for a walk in the woods a good blade is very useful.
A well made folder will be very useful and helpful, for instance a Spyderco Pacific Salt with a serrated edge is impervious to rust, has a strengthened tip, is lightweight, and has a good lock. Its great for slicing and dicing and at a pinch will be useful to assist in chopping bigger branches.
However to build a camp then a machete or kukri will be a much better choice, these will hack through most things with ease, will dig into the ground fairly easily if you need to hollow out some dirt/snow, Gerber makes a good machete that has a saw blade on the back, but forreal chopping an axe is a better option again. Once more these are heavy and probably not what you want to take for a walk.
A good fixed blade is your next option, and probably the best one there is overall: can still slice and dice, should be stong enough to open a can (although a can opener is much better-this is emergency use not everyday) should be able to be tied to a stick as a spear or for cutting things out of reach, is strong enough to be put edge down on a big branch and then hit or pounded with another to cut it, should be able to be used for light digging use, should be fine enough to skin and gut as well, needs to be able to hold an edge, but should also be able to be sharpened on a rock if you do not have a proper stone with you. Point is often a weak point-for this I avoid the "bowie" style, tips often break, I prefer a tanto tip, very strong.
Length: too big and you will not have it when you need it, too small and a folder is better, overall around 12 inches, blade 6-7 and handel remainder. A good sheath is needed, might be better to get a custom made one if the one it comes with is no good, and if you can put a bit of flint in it somewhere then thats a bonus too, some have a little pouch for a sharpener, throw away the stone and put together a tiny kit with a ceramic sharpening stick, a bit of flint and a striker, needle and tweesers, minimum bits and pieces in a tiny in or wrapped in tin foil.
If you can wrap some paracord around the sheath as well this will be useful.
Remember though - it needs to be with you to be useful, if its too big you will leave it at home that one time you go for a 5 minute walk, see something funny, take a wrong turn, and actually need it...
