the knife that has impressed me the most is my spyderco chinook II. come to think of it, most spydies impress me. i was not a fan of them, until i bought an endura at gander mountain some years back. i have been hooked ever since. i was a cold steel fan until then.
as far as karambits go, i have a few from different makers. i had an emerson, but sold it. there's no questioning the quality of emerson knives, i just detest one sided chisel ground blades. the spyderco version has a great blade profile, but the handle is too flat & wide for my taste. the mantis karambit has a better overall shape, but, again, flat chisel ground blades irritate me. so did the sharp edges of the handle, and the poor finish. so far, my favorite k-bit is the 5.11 journeyman. it seems to combine the best features of all the others, great blade & handle profile, nice contours, quality blade steel, and reliable. that's the one i'd recommend to anyone wanting a production karambit. you can find them for under $100 most places.