Carried a knife for years. Had a hard time carrying one in the Navy though. Since I was in aviation all the tools had to be accounted for and pocketknives and multi-tools didn't get carried a lot when we were working on the planes. I lost my small Leatherman one time on the flight line (where the planes are) and I knew exactly where I dropped it, but they made a big fuss about it anyway.
I have a little single blade Gerber now that clips right inside my pocket. Easy one-hand operation and it has been a screwdriver, pry-bar, toothpick (I wash it periodically), splinter remover, scraper, whittler, cutter, saw, you name it. It's about as useful as ducks are cute....
And if anyone watches Survivorman, you know how useful a Leatherman is. Go Les!