And the one quite some years back, regarding the use of a particular brand of microwave oven, which included in the 'Warnings' section of the Instruction Booklet "Must not be used for drying dogs or other household pets."
This was because some stupid women stuck her Poodle in her microwave, to dry it after bathing it. Of course, the dog ended up a very dead hot dog.
She sued the company concerned, and won, as the instructions did not warn against this particular danger.
And of course, the use of a bayonet, which must not be allowed to become rusty or contaminated, as this may cause infection to the person stabbed with it. The same reason for stainless steel ball-bearings in the Claymore .