I'd venture to say that the most common categories are:
-- Dress Knife
-- "Work Horse" Knife
-- Kitchen Knife
Then there are categories that seem more specialized, such as:
-- Marine Knife
-- Bushcraft Knife
-- Self Defense Knife
-- Military/Tactical Knife
-- Rescue Knife
Yet personal EDC needs are often more specific or specialized than the arbitrary EDC categories we come into contact with. I've mentally catalogued my EDC rotation into a number of categories that I shift between, depending upon what I expect to be doing. For me, those categories would be:
-- Fishing Knife (usually a smaller knife in the salt series)
-- Chore Knife (for cutting around the house, indoors)
-- Trail/Hiking Knife (A fixed blade, and a larger folder usually meet my needs)
-- Oil Spill Response / Marine Knife (It's gotta be a salt... and serrations are in order)
-- Dress Knife (for those days I'm a bit more dressed up and not out and about, I carry a dressier folder)
-- Dress Knife Plus (something that comes out on the most special occasions... holidays, fancy dinner parties, etc.)
-- Emergency Self Defense
-- Socially Acceptable Cutting (something small and not-too-flashy, like a dragonfly)
-- HAWKBILLS!
-- Kitchen Knives
It begs the question... design fewer knives that meet more needs? Or a higher number of knives that meet more specific needs. Less designs that do more, or more designs that do less?
What about "more designs that do more" ?
Spyderco has always done an excellent job of thinking outside the trap of arbitrary EDC categories. Verily, they've INVENTED EDC categories... the Slip-it is a great example... so is the "little big knife." They've also pinpointed and met specific needs of specific groups of people... the Jumpmaster is a great example. They have also challenged our "Western" ideas of what a knife should be like by offering exciting designs from around the world (Barong, Kukhri, Chokwe, Persian...). Jason Breeden did an awesome job of designing a knife that defies categorization, and meets specific requirements of his outdoor adventures in the Appalachian mountains (all hail the Captain!).
About 10 years ago, in the mainstream music industry, the hot trend was creating what producers called a "mosaic" type product... something that considers existing boundaries and genres, and attempts to meet multiple "specialized" expectations. If we applied the same concept to knives, we'd come up with interesting and challenging possibilities, such as:
-- A marine knife that could also serve as a gentleman's dress knife
-- A socially-acceptable emergency self defense knife
-- A hawkbill for hiking
-- A knife fine tuned for both self defense and rescue tasks
-- A dress knife for heavy chores
-- An emergency SD slip-it
-- An oil spill response knife well suited to the office
-- A kitchen knife for hiking
Just a few examples. In different countries and cultures, there are many other EDC categories.
I learned a while ago that some of the most unlikely pairings of concepts can ultimately prove to be some of the most successful.
Lots of my outdoor fixed blades double as kitchen knives... my girlfriend likes using them more than using "regular" kitchen knives.
Anyway... what this is all boiling down to is... I'm curious what other people's personalized EDC categories might be? :D