I'm something of a collectors, or perhaps more accuratly an "accumulator" as some others have said. I certainly have more knives than I really need. I find knives in general interesting, so my "accumulation" is rather broad and unfocused.
Modern Pocket Knives - Benchmades, Kershaws, and especially Spydercos. All various types of stainless, with pocket clips and thumb holes, studs, or some kind of AO. These all see regular use as EDC.
Outdoor Knives - Bark River, Marbles, Cold Steel, Case and a few customs. Fixed blades, in a mix of stainless and carbon steel. Mostly in the 4-5 inch range but a few larger and smaller. These see regular use on camping trips or weekend outings.
Slip Joints - Mostly Case, with a couple other brands. Traditional patterns, lots of carbon steel and a few stainless. Sizes ranging from Peanuts to big folding Hunters. Again, these are all users, some as weekday EDC some as weekend carry.
Tactical - A fuzzy term I admit but these are all fighting and combat knives. Cold Steel, CRKT, Gerber, Boker, Ka-Bar, etc. Bowies, Daggers, Tantos, and a few more exotic designs. These are the only one's I really don't consider "users" (as I seldom get into knife fights) but have always had a certain facination for me.