Without a doubt I absolutely love my Spyderco Paramilitary 2. Once I've spent a few days with it (I just got it today in the mail) I see huge potential for my new Spyderco Endura 4 but believe it or not, in what will likely be a close tie for second place I'd have to say that I absolutely love my Spyderco UK Pen-knife. I also own a Spyderco Byrd "Flight" which is a very good knife and exceptionally good for it's low price but what keeps it out of the running is that it's rather heavy. It'll carry an edge like nobody's business and holds that edge pretty well.
Edit: Correction, the Spyderco Byrd is actually a Cara Cara plain edge. Very solid, attractive and smooth action knife.