There are few objects more iconic than the Swiss Army knife. The blue scales on mine don't match the classic red or silver you probably imagine, but it is a genuine Victorinox.
Pictured with it for reference are an original Leatherman PST and a Buck 110 folding hunter. Folding knives seem to have been used for 2500 years or more based on archaeological records. Some surprisingly early finds have had multiple blades and various other tools included. I double-checked Wikipidia's citation of Herman Melville's Moby-Dick, and that novel does indeed mention pocket knives with,
...not only blades of various sizes, but also screw-drivers, cork-screws, tweezers, awls, pens, rulers, nail-filers, counter-sinkers.
The Swiss Army knife is thus just one example of a design trend that predates it by many decades at least. Only the Leatherman seems a uniquely modern invention. The Buck is in essence the same as tools used by the ancient Romans.
So why "Swiss Army?" I wondered what it was about the Swiss and their army that gave a name to a pocket knife with extra tools. Why did they set the standard? I poked around a bit on the web, and it seems that in the late 19th century, the Swiss Army decided a special tool should be issued to their soldiers. The resulting design was approved in 1890 and first issued in 1891. It had a knife blade, awl, screwdriver, and can opener.
The sources I read say a screwdriver was needed to maintain the Schmidt-Ruben rifle of 1889. At first, it seems production of this knife pattern was outsourced, but a Swiss entrepreneur began making them domestically and supplemented sales with an improved Schweitzer Offiziers und Sportsmesser (Swiss officers and sportsman knife) design that became a commercial success. His company would eventually become Victorinox. This company and their competitor, Wenger, split retail and military production until they merged into one unified brand in 2013.
But how did this tool come to be such a global icon? It wasn't the first, after all. The internet suggests soldiers returning from World War II brought these multi-tools home, and post-war demand created economic opportunity. The Swiss also have a reputation for quality and precision in watches and firearms. As a neutral nation, they avoided engendering any global hostility during either of the World Wars. Any and all of these factors could have been what brought these tools to a global audience.
My knife is essentially the revised 1961 military model with the addition of a center saw blade, called the "Farmer." There is a wide range of Victorinox models with numerous other tool options, so you can find one with almost any feature you may need.
I personally prefer to carry a dedicated single-blade pocket knife with a spring-assisted opening mechanism and a Leatherman multi-tool for other tasks, but a Swiss Army knife is a great addition to any emergency kit, tackle box, or backpack. It is one tool that can do a lot of things without taking up much space or adding much weight, and that is often a good tradeoff for the slightly more cumbersome thumbnail slots to access the tools, or the lack of a serious lock mechanism for the blade. Some countries or smaller jurisdictions also may prohibit my preferred tools, so the Swiss Army knife is often a good option to avoid being a lawbreaker if that concerns you.
For what it does, and for the price, it's a good investment. Plus, if it's good enough for MacGyver, it's good enough for any of us, right? Just don't go crazy and order a Wenger Giant Knife with almost every tool ever built into one giant slab of sandwiched stainless steel.
You can find out more about the various versions of this knife at the Swiss Army knife wiki.