Since everyone else has done one, I suppose.
I own a wide variety of knives but currently what I carry with me every day is one of these:
CRKT Desert Cruiser.
I picked several of them up for a quite good price, so I have one in each car, one in each bag (I carry a laptop bag when I’m working at the library and a Maxpedition FatBoy Jumbo other places) and one I toss in my pocket. It’s a decent knife – no spring assist but there are both ambidextrous thumb studs on the side of the blade and a raised ridge on the back that make it very easy to open. The handle is comfortable and fits my hand nicely. I like the partially serrated blade and it holds an edge even with heavy use.
I keep a variety of multitools around, primarily Leatherman and Gerber types – I really need to pick one up for each car. I have one in each bag and one sitting next to the CRKT folder I carry in my pocket.
It’s not overkill, I swear 😉