I admit to doing a double-take when I saw a guy with a slung katana picking up some groceries in the main station, but nobody else seemed to care. “Guy with a sword getting a liter of milk and some eggs. Meh.”Of course, the Swiss culture is pretty alien to me in a lot of ways. The very sight of the weapon in public is subconsciously tied to “Oh, this person is a participant in some organized and/or sanctioned activity.” And if there's anything to which the Swiss respond well, it's organization and sanction.
Even rather unusual things, like the guy wearing a full-body ghillie suit with a rifle slung on his back buying a cup of coffee from the McDonalds, go completely unremarked-upon by anyone here.
If you had a flamethrower, they would probably just assume that you were a licensed flamethrower owner on your way to your flamethrower owner’s club’s mandatory monthly practice meeting to keep your flamethrower certification in good standing.