I take a Swiss army knife. I use the blade to slice food and cut rope. I use the can opener to...open cans. The tweezers are nice for splinters, and they've also pulled out some things from my tires that caused flats.

I brought a Buck sheath knife on my first couple of tours. I felt cool with it on my hip (I was young) and felt a little protected, but I have a problem with carrying too much weight so I concluded the little Swiss made more sense.

The pliers on a Leatherman are very attractive, but looking back I can't remember any situations where I absolutely needed pliers. Plus I have this weight problem. Aren't Leathermans heavy?