Chekhov's Gun
"The Room", by Tommy Wiseau, is a movie where Chekhov's gun isn't applied. It contains lots of small happenings with no further relevance. It has lots of other issues, technically speaken.But together they make this film not only amateurish, but it also gives it a certain kind of realism. In real life stuff happens and still may have no further relevance to the "story" after all. In real life there is nobody enforcing Chekhov's gun.Together with the other charming mistakes and bad acting the film feels quite authentic. It gives this impression that someone just wanted to tell his story, despite not being as professional as we are used to. 
Like a little child coming home from playing in the woods that excitetly blabbers out the story of what he just experienced.