If you only carry one knife to take on all of those myriad things you would reasonably want a knife to do, it should be this one, the Spyderco Dragonfly 2. I realize this is a bold and, for some people, a controversial claim. But I have my reasons.
Knives are the oldest purpose-made tools. Other primates make tools, chimpanzees most specifically, but the tools they use are not shaped by them into forms that are not natural to the materials they use. Nor are those tools used in conjunction with other materials to enhance the tool's effectiveness.
Jane Goodall discovered that chimpanzees use various objects as tools – stems, twigs, rocks, branches with stripped off leaves – to accomplish certain tasks, and occasionally as weapons. But these are simple objects picked up in their immediate environment and occasionally slightly modified. Branches with leaves stripped off are used for various purposes, rocks are used to smash objects and leaves may be chewed in order to act like a sponge for getting at water. But chimps are not carving sticks into shapes as tools, or chipping stone to obtain a cutting or scraping edge with a further view in mind as a tool. Only humans, very early humans, did this. And what they made were at first simple cutting or scraping edges from suitable stones, then they began to modify those edges into more efficient shapes and applied wooden and bone handles for more varied and efficient uses.
The most fundamental tool that resulted from this was the knife. So, this is a good point at which to attempt a definition of "knife".
The standard dictionary definition is: a cutting instrument consisting of a sharp blade fastened to a handle
That definition is fairly standard for knives today, but it is really not suitable as a general definition of the knife as the first tool. Why? The use of the terms blade and handle refer to relatively modern additions to the fundamental cutting instrument that was in use by our ancestors for a few hundred thousand – if not a million – years before someone began fashioning the edge at the end of a blade, and attaching a handle to it. The earliest cutting and scraping tools we know of, the Oldowan toolkit, were made by australopithecus africanus and dates from over 2.6 million years ago.
The Oldowan tool kit is composed of hammer stones showing battering on their surfaces, stones, called "cores" exhibiting a series of flake scars along their edges, and the sharp stone flakes that resulted from the cores being struck by the hammer stones. There is also evidence of actual pressure flaking, which is different from and more precise than striking a core in order to remove flakes. By around 1.7 million years ago, humans began removing very large flakes from the core stones then using these thin and longer flakes as blades with their edges sharpened by striking or percussion flaking techniques. These, and certainly the larger and cruder sharp stone edges that were manufactured were knives in the functional sense of the term. Once someone attached a handle, the "modern" knife was born.
To paraphrase Sal Glesser, knife designer, owner and founder of Spyderco knives said, the knife is all about the edge. That is what a knife does, it cuts things. It cuts with the edge, or with the point which is really just a termination of the edge. Now, I am not a knife designer but I have used and been around knives in various capacities for well over sixty years and I agree with Mr. Glesser that the edge drives the design and eventual efficiency of a knife.
Sharp edges cut things. There are many and varied things that require cutting, so it stands to reason that for the most efficient cutting the edge must be compatible with the cutting requirements. Slicing a large piece of meat demands different edge requirements than cutting a half-inch, wet manila rope under strain. Filleting a good sized fish requires a different edge than punching through and cutting a piece of dry wall. The edges must also be able to withstand the strain and abuse of the materials they may be used on, and, if it is a good edge, will last through the job without the need to be replaced or re-sharpened.
In order for an edge to last for an appreciable time, it must have something to support and maintain it, hence the blade. Blades have their own requirements which are tied to the intended use and function of the edge – should blades be thick or thin, long or short, heavy or light, maintain the edge under impact or pressure, provide long use without dulling? These are only a few of the considerations a knife designer must work with.
Oh, then there is the handle. Design, materials, type of carry, ergonomics... all of these must fit in with the other design elements that are driven by the edge.
Combining all of these elements into a purpose driven knife is not easy and requires understanding of all of these characteristics and demands, as well as expertise in metallurgy and materials engineering. It also helps to have a love of knives otherwise the end result may be just an ugly piece of machinery when it could have been a highly functional piece of art.
Now, back to Spyderco's Dragonfly 2. Why is this the one knife you should carry if you only carry one? The Dragonfly 2 embodies all of the elements discussed above expressed in modern materials, manufacturing techniques, ergonomics and value.
It weighs only 1.2 oz (34 grams) so it is not a burden to carry on your person. The edge is right for cutting almost anything at 2.25" (57 mm) in length, ground in a smooth curve terminating in a strong, almost needle-sharp point. The blade is thin at .093" (2.5 mm) yet made from excellent VG-10 steel which is durable, sharpens easily, holds an edge for an acceptable period and is light weight. The leaf-shaped blade harkens back to those early, primitive stone cutting tools (I'd say it is a time proven shape having been around for over a million years.) The handle is so shaped that it will fit hands small to large and made of almost indestructible material moulded with a non-slip surface.
I watched an experienced fisherman, as a demonstration, fillet an 18" mackerel with a very sharp folding knife that has a blade with a 1.4" cutting edge. I mention this to point out that with a blade about twice that long, the Dragonfly 2 should be able to do most anything a reasonable person would require of a daily carry knife.
And, even better, it is very inexpensive for an excellent folding knife made of superior materials.
I'm working on my third Dragonfly 2 now. I lose them, I buy another. I lose them because I always carry one with me, and sometimes, being human, I forget things, or things happen. I figure that's a small price to pay for the best all-around folding knife on the planet.