Victorinox Outrider SAK A not overly tough locking blade and a usable saw. Paired with a quality 4" fixed blade (many to choose from) or a small axe and you've got lots of bases covered.
I have one of these in my BOB, it is a great knife in a good sized package. For about half the price of a Leatherman Wave, it covers most of the same fuctions I choose the Wave for. While not a replacement for a good sheath knife, like most if not all multi-tools, it is a great knife!
I don't think there is any one perfect survival knife, I choose mine based on my experiences and needs. Even then, I choose to carry a minimium of two knives in the field with me, a good multi tool (like the Wave) and a good fixed blade or Sheath knife.