It's an absolutely fascinating question made more so by the fact that man is the only animal that uses a knife (excepting claws, teeth, etc.). In fact, tool use is something that really separates man from the rest of the animals.
There are very vague examples of animals using simple, found tools. A sea otter, for example, can sometimes be seen pounding with a found rock to open a shellfish. But there is a huge difference between pounding with a found rock and pounding with a Stanley Claw Hammer much less pounding with a hydraulic power hammer. And yet pounding with a found rock is a fairly sophisticated example of non-human tool use.
I've heard anthropologists point out that some monkeys will pick up a stick, break off the branches, and then poke the stick down into an ant hill causing the ants to climb onto the stick from which the monkey can then eat them and saying that that is an example of making a tool. But even if we do concede that as making a tool, it is lightyears away from even making that simple claw hammer mentioned above.
Man is totally unique in the world, set apart dramatically and definitely, in that he purposefully designs and makes tools and that he purposefully and skillfully uses them.
Man's first tool was probably a pounding tool. He may have used a found rock to pound open a shellfish. But, man did not stop there. Man was not satisfied with finding a rock and pounding open a few clams. No. Man -- and man alone -- asked, "How can I make this better?" Even without knowing about levers, he somehow intuitively figured out that if he somehow attached the rock to a stick, he could pound harder with it.
Maybe, just maybe, in all of that pounding, he chipped off a piece of rock that had a sharp edge.
Rocks sometimes break naturally leaving sharp edged. There are occationally naturally-occuring knives just laying on the ground. But man alone picked one up and figured out how to use it.
Maybe, when his hammer head broke, he picked the pieces up. Maybe one of the pieces cut him. But man did not react defensively. He did not conclude that the rock had attacked him. He did not perceive the rock as a danger. Instead, man perceived it as something of potential value. He may have even tried to make more of these nifty rocks by pounding more. Over time, he figured out that some kinds of rocks work better than others and he developed techniques to get the best edges. And then he designed a tool, a sharp rock mounted on some sort of handle.
No other animal has ever done this. No other animal has ever made this leap.
So, when we celebrate the knife, we celebrate man's uniqueness in the world.
I am man, the tool maker, the tool user.