I carry a few.
My main "utility knife" is a traditional folder or some sort, with multiple blades. Like a stockman. Something with both curved and straight blades.
My secondary "work" knife is a Spyderco Tasman Salt (plain edge). At work it's supremely useful in cutting open boxes, breaking down boxes, and opening plastic bags. Occasionally (rarely), I'll substitute the Tasman Salt PE with an Atlantic Salt (serrated).
I always have my Victorinox Cybertool 29 on me, although more for the other tools than the knife blades themselves. The multi-bit driver is perhaps the most useful thing I carry, even moreso than any knife blade.
On my keychain I have a Leatherman Squirt PS4. It has a blade, but like my SAK, that's more an afterthought considering the other tools (pliers, scissors, etc).
I also have a Leatherman Charge in my backpack. Again, more for the tools than the blades, but if needed, there's 2 excellent blades at my disposal (plus a diamond file I can use to sharpen other knives in an emergency).
Finally I also carry a Spyderco Endura Wave SE. That's the knife I hope to never use for its intended purpose.
Best of all, I can carry all of these without looking like Batman with a utility belt, or like some mall ninja decked out with tactical gear. Apart from maybe seeing the Endura clip sticking out of my pocket, you'd have no idea I had so much preparedness on my person.