Everyone makes a good point, but here is how I feel about "my knife".

It has to be cheap enough that I'm not worried about loosing it or damaging
it doing the urgent but unconventional task, like prying something open..

It must keep a fairly sharp edge. Often a expensive knife can be made razor
sharp but the first time you cut a synthetic line or have to scrap a little
paint off something (unconvential task), the edge is nicked or dulled. I
generally go with a utility edge that cuts well enough for line splicing,
etc. (but if I want to shave my arm, I'll get a razor).

It should have some utility tools built in so you don't abuse the blade. But
let's not go overboard with the tools.

My personal knife is a West Marine SS (but it's magnetic for some reason).
It has one wide blade, a marlin spike, slotted tool for turning shackle pins
and a flat piece sticking out of the cheeks that server as a screw driver. I
don't think I paid more that $8-10 for it but that was over 10 years ago. My
kid have given me the expensive, fancy tool kit in a knife but they have
been to heavy and bulky to keep on my pocket. If you opt for a sheath on the
belt, sooner or later you will get tired of strapping it on and won't have
it when you need it. I always end up carrying the knife I discribed
previously when on the boat or when ashore.. I have a habit of checking that
it is there everytime a move from one place to another (kinda like when you
check for your glasses or wallet). Just part of my attire..

A knife like this meets all of my requirements without weighting me down or
wearing holes in my pocket. If I need tools, I keep a few in the cockpit
(away from the compass) and even more in a lockers down below.

A final note, as long as I'm on the stump!
Every crew member should have a knife and if they arrive onboard without
one, have a few good ones, like mine that you can offer them. Then remind
them that they should get their own at the first opportunity.

I know I don't want to loan my knife, not because it is anything fancy or
I'm afraid they might damage it, but because loaning it out would mean I
wouldn't have it with me and that is like loaning glasses or wallet.

Now for my usual disclaimer:
My opinion and experience. FWIW

Steve
s/v Good Intentions