Am having trouble deciding if you mean "the one Spydie" that I would choose if I could only have one, or the one that best represents what Spyderco's knives are about.
If it is the one that best represents what Spyderco knives are about, then the one I'd choose for that category is the Native FRN. (Tho I have to admit that the Endura and Delica may deserve that role.)
If I could only choose to have one Spyderco, it would be my Wegner for sure.
Can't stop without saying that maybe the Shaparia best represents what Spyderco is about. I am certain that no other company would have produced such an unusual looking knife. Spyderco is willing to take chances, to go with something unusual or odd, or whatever. That's why its my favorite manufacturer.