Imperial, adjustable, left handed wrench. Or left handed any common hand tool (hammer, spanner, screwdriver…). Muffler bearing. Light bulb for the crank case. Blinker fluid. The list goes on.
And, within reason, I think those are pretty decent pranks. No one gets hurt, many get a good laugh out of it, including the one looking for a two headed hammer if executed properly.
I’ve used Seafile for years just for this. I haven’t ran that on pi, but on virtual machine it runs pretty smoothly and android client is pretty hassle free.