Single use rulers -- now I don't take a class if I have to buy a special ruler for the class. Blade sharpeners -- I have had several and they all got donated. Fancy needle threaders -- haven't got any of them to work so I use the little silver one that I have been using for many years.
I did not buy it, but I wanted to take a class to do a quilt out of a book I had and was told that since I did not buy the book at the shop I had to buy it again (decided not to do the class).
Incidently, I love the shape cut rulers -- I use them all the time.