I'm really a folder kinda guy andd have been paring down my collection to a few high end gent's folders (William Henry) and plan to own no more than 7 or so customs. Of my four custom folders in my collection, the most perfect has got to be the Scott Cook Lochsa. While it's a bit big for my workday needs, if I could only own one, it would be the Lochsa.
The fixed blade is a tough one for me as I don't know much about them. I only own one, a < $20 CRKT Carson designed F4 that I use as a letter opener, albeit a very sharp letter opener. If I had to choose a fixed blade, it would likely be something small (3" blade length or thereabouts). Makers that come to mind that I've thought about owning include something by Mike Snody, Scott Cook (the small Owyhee hunter, perhaps) or Bob Dozier.
Again, a tough but good question. It certainly gets me thinking.