You know the sort of thing, Long Weight, Glass Hammer (they actually exist), Left handed screwdriver etc.
We had a young lad in the workshop once who noticed some wooden dowels on top of the big oil fired heater in the corner, he asked "What are they for", I told him they were for wood welding, he scoffed for a while until I told him that for the welding to work properly they had to be very dry, that's why they were on the heater. He was still scoffing and pointed out that wood was an insulator and wouldn't conduct electricity, I told him that when you were ready to weld you dipped them quickly into a bucket of water and struck the arc, once the arc was established the wood turned into a liquid state which would conduct the electricity being conducted down the outside through the thin film of water and therefore you could weld wood.
He walked away convinced that he'd learned something new, it was weeks before he found out.
I also sent a young apprentice to the stores for a 9 inch Whitworth combination spanner, he came back after about an hour saying that the storeman said to come back and ask if a 10 inch one would do, I sent him back to ask the storeman to order one, the storeman played along for about a week giving all sorts of excuses why the spanner hadn't arrived.
The things you do when you're bored and fancy a laugh at work!