Annoying items to me.
The infamous automatic revolver in detective stories from years ago. There was such an item, the Webley-Fosbery. It was a collectors item by the time the mysteries were typically written. It was from the early 1900s and always quite rare.
https://en.wikipedia.org/wiki/Webley...matic_Revolver
Also until very recently book mention of safeties on revolvers. A very recent addition to some.
Shifter stories where there is a gain or loss of mass from the shift. Where does the mass go when a 200 pound man shifts to a 100 pound wolf? Per physics it sounds like a hell of a explosion as mass is converted to energy. About like a hydrogen bomb, a big one. The same problem for going the other way. Where does the 100 pounds mass equivalent energy come from? From a physics standpoint only Poul Anderson paid attention to this in a couple of fantasy novels that I am aware of.
How about ancient or medieval stories where at a meal they mention foods that were not known in the location and time. An awful lot of foods common world wide today were unknown in ancient or medieval Europe and North Africa before Columbus. If writing a historical novel, do your research.