Anton Pavlovich Chekhov was a Russian playwright and short-story writer who is considered to be among the greatest writers of short fiction in history. He produced four plays, and his best short stories are held in high esteem by writers and critics due to his dedication to elevating the quality of the genre.
Chekhov's Gun is a dramatic principle that he ascribed to where he stated that everything irrelevant should be removed from a story, leaving only elements that are vital to plot points. He argued that it was wrong to make 'false promises' to the audience by showing things that never lead to anything in the story. It has come to be accepted as the occasion when a seemingly inconsequential object or event in a movie is later revealed to be of important significance.
The James Bond franchise uses this concept repeatedly, with Q demonstrating his clever new gadgets to Bond at the beginning of each film, and every feature encompassed in them coming to his aid later on in the story. The idea is very satisfying for the viewer, as it means a twist ending has been properly set up and is earned, not coming out of nowhere.
There are many examples of movies with Chekhov's Guns, but here are 10 of the best (warning - spoilers).