Lots of folks are into multifunction "knives". Every time I try one I quit carrying it after a while. Don't know how many times I've started carrying leatherman type tools and stopped, but I always have a single blade folder with about a 3" blade in my pocket.
I like the reasonably sized Swiss Army knives like the Officer and Farmer. Heck of a bargain at under $40. I carry those while camping/hiking and find them useful. Fairly light, so don't pull my pants down when in my pocket. The large multi-tools, not so much. Too heavy/bulky for me. Nice to have in the glove box though.
I also have a ~3" single blade locking folder clipped in my pocket every day. When I have to cut something that doesn't want to be cut, I want a sturdy purpose-built tool to do it.