My primary survival knife is the one I ALWAYS have on me. Wilderness, urban, day, or night.

In my case, that is a Byrd Robin these days. In the past it was a Spyderco Native, but I've grown to like the less expensive Byrd Robin even better for day-to-day carry.

When I go out into the winderness I usually suppliment my primary survival knife (not replace it, supplement it) with something a little bigger. That may be a Mora Clipper or a Cold Steel SRK. Whichever I feel like lugging around at the time. The SRK is pretty heavy, so mostly it says at home while the Clipper gets to go. I bought the SRK only because it was on sale, a factory second, a long time ago ... $29. Couldn't resist at that price, even if it was a Cold Steel (a fairly low-end knife), but honestly it doesn't get much use.

I don't have a dream survival knife, because I think the ones I already have (although inexpensive) will do everything I could ever need.