Another Case which at least meets thread title, ....if it had come out immediately opposite (instead of only five years ago) the then new Spyderco Clipit and then linerlocks, they never would have taken off the way they did.
Case Trapper Lock with pocket clip. I was in the thick of those changes, and the new stuff was just ugly compared our work knives of accustomed use. BUT, we bought them due to unbelievable convenience of clipped to handy location rather than buried under toolbox and car keys in bottom of pocket, and miracle of one hand opening and closing while working on something which could not easily be let go of in order to close a knife.
EVERYbody wanted a knife able to be instantly opened, LOCKED open and why the 110 was IT back then, and the one-hand closing was just a miracle.
However, had a nice pretty bone handled single blade silky smooth jack with liner lock and pocket clip been available then, which IS the Case Trapper Lock with pocket clip, all those others NEVER would have gained traction. We valued looks, polished steel and bolsters, while today's buyer thinks sandblasted and painted is "quality", gun or knife. Sad.