My entire EDC system currently includes 5 knives, each for a different purpose. I carry:
-A folding knife with a blade length of at least 3.5" (the ones in my rotation are currently all Cold Steel blades and include a Voyager tanto, Recon 1 tanto, Code 4 spear point, Pocket Bushman, and Mackinac Hunter [soon adding a medium original Espada]), for general cutting tasks
-Cold Steel Super Edge on my keychain, for cutting certain foods and when I don't want to scare sheeple with the bigger knife
-The knife on my multitool (either a Leatherman Sidekick or a Victorinox Swisschamp), I don't generally use this, since I carry the MT for the other tools (and prefer the superior ergonomics, blade steel and lockup of a dedicated folding knife) but I may use it when I don't want to scare hoplophobic people and I need to cut something
-Cold Steel Survival Edge, in my backpack as a SHTF tool
-Cold Steel Kudu, in my backpack as backup
I used to carry an ESEE Izula instead of the Survival Edge but I found its handle to be too small and uncomfortable for my small sized hands, even with the canvas micarta scales. The handle of the Survival Edge is really nice in hand (hollow without being weak!) and the whole knife feels lighter, if you can believe that.
When I'm not at work I may carry my Cold Steel Spartan or AK-47.