My thoughts on this line up with most of the others, with an addition. Limiting yourself to one knife calls into play all the usual questions about minimal mission requirements for the knife, price you are willing to pay, materials & design considerations, consequences of under-knifing yourself, etc.
IMHO Busse blades are the best survival knives when chopping & other heavy work needs to happen. They are insanely tough, practically indestructible blades made expressly for beating. If I had to pick just one blade to take when mission requirements aren't certain (When are they ever, really?) I would take a Busse Basic 7 or Steel Heart. If the price tag for the Busses is a bit steep, for a mid-size knife I'd recommend looking at some of Newt Livesay's blades or the new Becker Knife & Tool Combat Utility Knife with its 7" blade & comfy handle. The Becker is $48 at Bayou LaFourche Knive Works.
http://www.knifeworks.com/product.asp?3=1630
For wood work I advocate taking a folding saw. So if there's no wood chopping to be done, then the Spyderco Moran drop point in 1/8" VG10 steel that others have recommended would be a very handy fish/food prep knife in camp. It is not very flexible, but that convex edge is scary sharp out of box & should hold up well gutting fish. It weighs just a few ounces & carries very conveniently.

You could easily wear it as a neck knife by taking the TekLok off the sheath to reduce weight. The Spyderco Morans are among my favorite non-Busse commercial blades.
My addition: Gerber Yari. Slightly longer blade than the Moran and slightly heavier. Blade is flat ground in 154CM steel with a very pointy tip. Its matte canvas micarta handle offers a solid grip, even when wet. Comments & links for the Yari here:
http://www.bladeforums.com/forums/showthread.php?s=&threadid=161841 It would be a bit heavy to wear as a neck knife and, as noted in the thread linked above, the standard sheath begs for tweeking or at least the addition of a TekLok to expand its carry flexibility. Nonetheless, with its lack of a guard I think the Yari would make a very reasonably priced and very handy camp kitchen knife.