Happened to me in med school with a pocket knife of all things.
School. Heh.
I carried an Benchmade folder every day of my life in high school (post Columbine, if I must date myself) in addition to a Schrade multi tool. Used 'em both for utilitarian purposes (even handed off the multi tool to a teacher so he could use it) and never got in trouble for it because I never went around acting like it was anything out of the ordinary. Though I did get a stern talking to in Brandywine for having the audacity to doodle a benzene ring in my notebook. Go figure.
Working the hardware store, I took to carrying one of my better butterfly knives as my work knife (because as "better" it still only cost me five bucks).
Lots of stuff needs cuttin' in a hardware store. Rope, tubing, tape, boxes, packages, you name it. We did get all types in there, from the usual soccer-momish type people ("My word, what you do need that barbaric thing for?") to military vets ("Neato, I got a couple of them.") to the section eight contigent ("Daaayum, dawg!").
I had a few people make a stink about it, but I just shrugged and said, "Hey, it's just a sharp piece of metal. I could have done it with a box cutter but what's the difference?" Most people couldn't come up with a coherent answer to that.
Some said "But that thing's designed to hurt people!" and I'd just reply "Is it? I just used it to cut you your rope. Can't somebody use a box cutter to hurt people?" There was also the contingent of armchair lawyers who felt the need to insist to me that it was illegal (only off of private property, bub) and wouldn't shut up about it.
But when I flipped that thing out, the best customers were the ones who would say "Wow, do that again!" or better still the ones who would whip out something even more garish/slick/tacticool and say "You call that a knife?"
People are weird.