The gun in the first act goes off in the third, and turns out to be completely useless. This is usually, but not necessarily, Played for Laughs
This is usually done with actual weapons.
- In Iron Man 2, Rhody is given a missile by Justin Hammer which is described as being incredibly advanced and powerful. Then, during the battle with Vanko, after a long, dramatic charge-up sequence, the much-vaunted missile pings harmlessly off Vanko's armor and sputters on the ground like a dud firecracker.
- In an episode of Family Guy, Quagmire is given a banana by Adam West who tells him "When the time comes, you will know". Later, when Quagmire is being chased by Cleavland, he hurls the banana at him. Both briefly stop and stare at it as if expecting something to happen before resuming the chase.
- Paul Blart: Mall Cop: An extensive sequence involves the character and some spicy hot sauce. In the climax, he spots the hot sauce again and flings it into his opponents eye. After a few seconds, the opponent recovers. Paul says, "Huh. I should have capitalized on that," and the fight resumes.
- In the Infocom text adventure of The Hitchhiker's Guide to the Galaxy, there is a Ravenous Bugblatter Beast of Traal killing gun you can find at some point. If you fire it at the Ravenous Bugblatter Beast, it emits a sad green ray that bounces harmlessly off the Beast's hide, and the game gives you a footnote: "It's not a very good gun, is it?"