Generally, a good fixed blade will do most tasks in the outdoors, and a good folder will suffice for urban survival.
I can recommend a few good brands, but I could narrow down the list even more if I knew what type of blade you are looking for, and how much money you are willing to spend.
To me, the best survival knife is one that you will have on you should you ever find yourself in a survival situation. For me that means a medium sized Swiss Army knife that I always carry, whether in a urban or wilderness environment. For the great outdoors that means a good fixed blade. The size will depend on the terrain and what I am doing.
For under $20 you will find Swedish Mora knives to be absolutely awesome. Generally speaking, I'd stick with a fixed blade knife with a carbon steel blade, for ease of sharpening, and for taking and holding a good edge in the field.
Look at the offerings by these great manufacturers and makers:
- Becker Knife and Tool
- Cold Steel
- Busse Combat
- TOPS
- Martindale
- Newt Livesay
- Marble Arms
- Bob Dozier
If you want a rust resistant blade and don't mind the increased difficulty in sharpening, definitely consider the knives by:
- Fallkniven
A good friend of mine has done some recent extensive testing on a bunch of outdoor type knives, and the overall best performing knife was The Busse Combat Natural Outlaw, followed by the Cold Steel Recon Scout.
If you don't mind the extra weight, definitely consider a good kukri.
Personally, my favorite survival knife would have to be a fixed blade knife with a full tang, and a carbon steel blade about 4-5 inches in length.
A good small fixed blade paired with a large chopper such as a bolo, kukri, machete, small axe, hatchet or such, is a combination that's hard to beat. Of course don't forget to have the Swedish army Knife in your pocket.
Happy hunting...