Ant-Man

Dr. Hank Pym, the original Ant-Man, (played by Michael Douglas) is trapped with his daughter in a building that is about to be destroyed.  They have no escape until Hank reveals that his tank keychain is more than it appears.  They burst through the walls of the building using the keychain because it was actually a real tank that he had shrank earlier.  Even the keychain part is expanded.  His keychain can be seen several times throughout the movie.  And in the early footage of the original Ant-Man that is shown a tank that looks very similar can been seen.  One must assume it is the same tank.

Payback

The head of the outfit gives his son a car for his birthday.  He presents him with the key and an engraved keychain.  Porter, played by Mel Gibson, taunts the mob boss with the knowledge that he kidnapped his son.  He offers to read him the inscription on the keychain and calls it sappy. 

A History of Violence

In the opening of the movie, two mobsters are on the run trying to lie low in small towns.  They are leaving their motel and their blue rabbit's foot keychain can be clearly seen. 

Mortdecai

Mortdecai, played by Johnny Depp, is trying to escape from someone trying to kill him.  He takes a car from his mechanic's while his man servant, played by Paul Bettany, holds off the assassin.  The keychain is the type in which a metal medallion is attached to a piece of leather. 

The Machinist

Trevor Reznik played by Christian Bale confronts the man who he thinks is behind a plot against him. His leather fob keychain can be seen.

Thief

In preparation for the upcoming heist Jim Belushi's character, Barry, is listening in on the owners of the safe for a password to turn off the alarm.  The owners of the safe open their front door and their keychain can be seen.  This type of keychain is hourglass shaped with a metal circle on one end.  There is a notch in the circle where the key is threaded onto the metal bar.

Mission Impossible Rogue Nation

In the beginning of Mission Impossible: Rogue Nation, Ethan Hunt is captured.  The literal key to his escape is on a rabbit foot keychain.  This is most likely a reference to Mission Impossible 3 whose plot centered around the mysterious "rabbit's foot". 

Sex and the City

Charlotte and her ex-mother in law, Bunny, are fighting over her apartment during Charlotte's divorce.  Bunny shows off her keys as proof of her ownership of the apartment.  Bunny has a solid metal bunny keychain.  Quite appropriate. 
From season 5 episode 5

Everybody Loves Raymond

Debra And Raymond are staying at a bed and breakfast to have a romantic weekend.  The bunny keychain on the room key is indicative of the cutesy theme of the bed and breakfast (much to Ray's dismay).

Supernatural

Supernatural has MANY keychains featured over the course of the long running show.  This first keychain is Dean's which is a bullet, it of corresponds nicely with the guys' lives as hunters.  It can be seen several times throughout the show.  This screen cap is from season 5 episode 18. 

From season 1 episode 15

From season 1 episode 16

From season 5 episode 14

From season 4 episode 7   The show features many keychains from the motels and hotels the guys stay at.

From season 14 episode 4   Toys are coming to life and trying to kill a comic book shop employee.  Sam and Dean figure out a ghost has attached itself to the keychain of the shop.  They dispatch the ghost after it inhabits a life size replica of a slasher villain.

Fantastic Four

In the trailer for the upcoming movie Fantastic Four, there is a very telling keychain.  On the rear view mirror of his car, Johnny Storm aka the Human Torch played by Michael B Jordan has a fire flower keychain.  The fire flower being the classic power-up from Super Mario Brothers.  Not only does this reference the human torch's power to control and emit fire but it represents the fact that this Fantastic Four is made up of younger people. 

Cast Away

Chuck Noland (played by Tom Hanks) has a swiss army knife keychain.  Right before his ill fated plane flight he gives Kelly (helen hunt) an engagement ring and his keys.  When he finally returns home she gives him the keys back.

The Hunter

William Dafoe's character, Martin, is just getting his assignment to hunt the, thought to be extinct, Tasmanian Tiger.  A key with a keychain can be seen as he going through his belongings.  It is a silver circle with the number 53 stamped on it.

Hook

Peter Pan (Robin Williams) visits tinkerbell at her home,  which is a cuckoo clock.  She has his personal possessions all around her including his keys and BMW keychain.

Z Nation

Murphy is desperate to get to California due to his worsening condition.  He tries to steal someone's car by biting them and taking their keys.  The man kept talking up his car and its upgrades while drunk in the bar earlier.  His skull key and paracord keychain matches the description of the ride.  From episode 7 Welcome to the Fu Bar.

The gang is using a white van which has a basic pink/purple fob.  Murphy steals the van, which is full of valuable oxycotin, at the end of the first season leaving everyone else to die.  From Episodes 12 and 13.

Criminal Minds Season 1 Episode 1 Extreme Aggressor

The real villain's keychain is revealed just as he is.  It is a metal z which represents his car.

Bob's Burgers Season 5 episode 5 Best Burger

Bob is competing in a best burger cooking competition on the wharf.  But he forgot to bring his special ingredient, black garlic.  He tells the kids to go back to the restaurant to go get it.  He tosses his keys to Gene.  His burger keychain can be seen.  It has been shown in several episodes.

The Andy Griffith Show Season 3 Episode 27 Barney's First Car

Andy's lovable yet gullible sidekick Barney Fife is trying to buy his first car but may in for a different ride than he thought.  The kindly old woman selling the car gives Barney her "husband's" keychain who also just so happened to be named Barney.  It is a white rabbit's foot keychain.  Barney is so nice he tries to refuse the keychain but she won't let him.

Family Guy season 13 episode 4 Brian the Closer

Brian is hiding at a hotel to avoid Quagmire because he tricked Quagmire into buying a crappy condo.  His room key with keychain be clearly seen.  He is staying in room 12.

The Simpsons season 26 episode 6 simpsorama

In this Simpsons/Futurama crossover episode the kids are putting things into a time capsule.  Milhouse puts a rabbit's foot keychain but bart didn't bring anything.  So, he puts his sandwich in there and it just so happens that the time capsule gets buried with toxic waste and the dna from Bart's sandwich combines with Milhouse's keychain to form a rabbit/Bart hybrid monster.  It causes problems in the future which sets in motion the crossover where the Simpsons meet the gang from Futurama.  It all starts with a humble keychain.

The Walking Dead Season 4 Episode 4

The group encounters some walkers in a auto shop and one of the members reaches for whatever is near.  In this instance it is a bathroom key with a screwdriver/icepick (hard to tell exactly) keychain.  Keychains save the day again.

Later Rick is prepping a car for a quick getaway.  They keys are in the ignition and the keychain is some kind of vinyl fob.  It is in the shape of the state of Georgia, which makes a lot of sense since the show takes place in Georgia.

Key & Peele L.A. Vice Sketch

In this parody of Miami Vice, Peele is going to drive the suspect they just apprehended to the police station but Key really does not think that is a good idea... 

Peele's purple rabbit's foot keychain can be seen for extended periods in several overly dramatic shots.

South Park season 18 episode 3 The Cissy

South Park satirizes some of the issues surrounding transgendered prejudice.  Randy Marsh is secretly the teenage pop artist Lorde so his place of work is unsure of how to handle the situation. Especially when it comes to which bathroom he should use.  They offer him a new private executive bathroom.  The keychain for the bathroom key is a fob with an E on it for executive.

Walking Dead Season 1 Episode 1

In the very first scene of the show Rick and Shane respond to a call of a police pursuit.  Rick's keychain can be scene and it is a plain white circle with some numbers on it.  Probably police issue since it is so plain.

Psych Season 4 Episode 8 "Let's Get Hairy"

A man goes to Psych thinking he is a werewolf and asks the guys to watch him during the night. They fall asleep and it seems the man escapes and jumps through their window leaving a tuft of  hair on the broken glass.  They take the hair to Juliette for her to test.  They keep it in a keychain coin purse.  Juliette says that she had one as a kid. 

The Shining

In the Overlook Hotel room 237 is NOT where you want to be.

Napoleon Dynamite

Napoleon's love interest Deb makes and sells braided lanyard keychains with other items door to door.  She happens upon Napoleon's house and forgets her case when she runs away.  She also gave Napoleon one of her keychains in another part of the movie.

In the Line of Fire

John Malkovich plays an assassin who wants to kill the president and Clint Eastwood is the only secret service agent who can stop him.  Malkovich's character builds a plastic gun in order to get past any metal detectors. But he still must worry about his metal bullets.  In order to get the bullets past security he uses a hollow rabbit's foot keychain with them hidden inside. 

A Goofy Movie

Goofy's car keys are on a gold keychain with the Disney logo.  An interesting fourth wall break.

Speed Racer

The key and keychain to the Mach 5 race car driven by Speed Racer.

Kirby: Triple Deluxe ( video game for nintendo 3ds)

In many video games there are collectibles to gather while you play the game.  In Kirby Triple Deluxe for the 3DS (released may 2014) the collectibles to get are keychains, 256 of them. Players can obtain key chains of classic Kirby sprites in levels and look at them from the world map.  Treasure chests containing key chains occasionally appear upon returning to the rest room. The game at the end of each level can also award a key chain.

This video shows every keychain in the game.  Thanks goes to the uploader.

The Real Ghostbusters

The ghostbusters must help the Fates get back their mystical shears which determine the length of mortals' lives.  They go to the netherworld to steal the shears back from demons but first they must get a ride from the ferryman Charon to cross the river Styx.  For the fare, the guys do not have 20 gold pieces, 40 silver pieces, a vase of purest bronze, an etching, or even a captain midnight decoder ring.  So Charon accepts what they do have, a rabbit's foot keychain and a cheese sandwich on white bread.  The ferryman is disappointed and would have preferred pastrami or roast beef.

From Hanging By a Thread Season 2 Episode 36

South Park: The Stick of Truth

From the video game South Park The Stick of Truth; when the boys help the owner of City Wok by defeating the mongolians (mongrorians) they receive the Mongolian Treasure Key which opens a treasure box.  The keychain which the key is attached has a picture of the Mongolian flag on it.

Other keys do not have keychains attached.  At least none that I can find.