Chekhov's Gun/Fan Works

• In Kyon: Big Damn Hero, Nagato checks Kyon's wristwatch in one chapter. Later on, it saves his life when he gets shot, turning into an armour... skinsuit... thing.
• In the 7th Sea story Homecoming, when her father Owen expresses his uneasiness about his daughter Colleen coming with the family to parley with one of the Sidhe, she just pats her guns, insisting on helping her grandmother Moira hunt down her (Moira's) hated brother. Later on, Colleen willingly shoots her father in cold blood with those same guns when she comes upon Owen trying to help his not-so-sinister-after-all uncle escape.
• Manchester Lost: Angelic singing kills demons. Who knew the whole climax was going to hinge on this little bit of trivia?
• In Axis Powers Hetalia fanfic Outcast Tino mentions putting a star shaped ornament on Flower-Eggs collar, it turns out it holds Torvald's crystal star.
• The Fan Verse, the Travelsverse, is basically one big armoury, with Instrutilus constantly placing guns in advance and using them stories later.
• Company 0051, a Halo Fan Web Comic: Master Chief is staying at the local military camp on Noiosi when he comes across a patch of forest with a large hole in the trees. The Captain tells him it was just a meteor. It was actually a shot-down Covenant starfighter which was carrying an AI.
• Test Of Humanity, a Portal 2 fanfic in which GLaDOS implants Wheatley's brain into a human body, has a scene where Wheatley ends up overeating and gains quite a bit of weight. Towards the climax Wheatley's overweight frame ends up being what causes GLaDOS to be defeated since it causes him to be stuck in an exaust pipe blowing up a good portion of the laboratory and tearing her apart.
• In the Law and Order Special Victims Unit fanfic Girls' School, Elliot sees his reflection in the window when he is at a crime scene. He later figures out that the main perp could be identified by searching the pictures of the crime, taken by the main perp's girlfriend, for any reflections in those windows.
• The original slash novel Captive Prince is notable for using a lot of those. Especially the earring comes to mind.
• In the Death Note fanfic Xanatos, L contacts Matt to help him with the Kira investigation after faking his death. As it turns out, L needed Matt specifically because he was the best person to convince Mello to work with Near, being his closest friend.
• Calvin's poker winnings from one episode of Script Fic Calvin and Hobbes The Series aid in defeating two electric-themed villains with Static Electricity.
  • And the 10th Anniversary Double-Length Special Edition Captain Napalm issue which helps Calvin and Hobbes find their way home in "Hypercube".
  • And Jack's auto-repair system that gets him back to Brainstorm's lab in "Robot's Day Out".
• Fallout Equestria has an armories worth