K is the king of brand names. K begins fewer than 1% of ordinary English words, but several of the world's top brands and companies begin with the letter: Kodak, Kraft, Kellogg's, Kleenex. Indeed, companies often deliberately misspell words that are normally written with a C or Q in order to be able to have a K at the beginning of their name -- Krispy Kreme and KwikFit, for instance.
K is a strong and powerful letter. It looks distinctive and cannot easily be confused with another letter on a sign or packaging (unlike O, C and Q, for instance, which all look similar, especially from a distance). It looks assertive -- like a person kicking out at someone or something. It's perhaps not a coincidence that the word kick begins with a K.
As an initial on its own it can stand for king, thousand or, in US (but not British) English carat, or karat, the unit of weight for gold and precious stones. These are all positive associations.
Unless K is followed by an N in English, in which case it is silent, it is always pronounced the same, again, unlike C, so customers generally do not have any difficulty pronouncing it. In German, northern European and Slavonic languages, K is a common sound, and the letter K is used more frequently than C.
K is a powerful sound. It is what is known as a plosive (others are B, D, P and T). When you pronounce a plosive, air builds up in the mouth and is then released all at once to form the sound. You cannot make the sound of a plosive last for several seconds as you can with the sounds M or S, for instance. This makes words beginning with K and other plosives more likely to register with the listener and more memorable.
There are just one or two negative issues surrounding the letter K, although they won't affect most businesses. Three Ks together suggest the Ku Klux Klan, and because of this K occasionally replaces a C in words to suggest a racist or fascist link, for instance writing America as Amerika.
We must ultimately thank the Phoenicians for our alphabet. They had a symbol called kaph, which resembled an open hand, and which represented a K sound. This was adopted by the Greeks, and named kappa, and then the Romans, whose alphabet we still use. The two short strokes of our modern-day letter K are a hark-back to the fingers of the original Phoenician symbol.