In the very first show of our first season ("The Man Trap" by George C. Johnson), we needed some salt shakers because we had a creature that craved salt. We had a story point which required the creature (disguised in human form) to give himself away when someone passed with a salt shaker on a tray. This posed a problem. What will a salt shaker look like three hundred years from now? Our property master, Irving Feinberg, went out and bought a selection of very exotic-looking salt shakers. It was not until after he brought them in and showed them to me that I realized they were so beautifully shaped and futuristic that the audience would never recognize them as salt shakers. I would either have to use 20th-century salt shakers or else I would have to have a character say, "See, this is a salt shaker." So I told Irving to go down to the studio commissary and bring me several of their salt shakers, and as he turned to go, I said, "However, those eight devices you have there will become Dr. McCoy's operating instruments."
For two years now, the majority of McCoy's instruments in Sickbay have been a selection of exotic salt shakers, and we know they work because we've seen them work. Not only has he saved many a life with them, but it's helped keep hand prop budget costs low.