A (very expensive when bought) document feeder on an HP scanner ruined when somebody tried to feed paper still held together with paperclips through it. By then spares were impossible so the feeder was trashed.
The there was the company that though it would save money by reusing paper in the fax machine. Quite why someone felt the need to Tippex out something on the "clean" side just to reuse 1 sheet is beyond me, I did point out that the cost of a single replacement toner/drum for the unit would keep them in paper for a long time but fortunately a quick clean with 1,1,1 Trich* did the trick.
Reusing label sheets in laser printers is always a recipe for disaster of course, although possibly not so much these days. I've had to peel a few stickies off drums before now, generally they've got away with it but I recall there was one that didn't.
*That probably dates how long ago it was!