Have you not given thought to a fixed blade knife yet? Sure that foldable knife in your pocket is great but in a survival situation you need something with a little more oomph. This article is a look into finding the right camping knife but I think the needs and expectations of that knife are very similar to that which will be needed in a survival scenario. The author describes just what you are looking for to a T.
There is also a great selection of three knives that are recommended to the reader. You will find a great section on the sharpening of that knife as well. This will be a very important part of this whole process. No matter how well you choose your knife, without a sharp blade its not gonna get you very far.