Strangers on a Train Plot Murder

"A couple of fellows meet accidentally, like you and me. No connection between them at all. Never saw each other before. Each of them has somebody he'd like to get rid of, but he can't murder the person he wants to get rid of. He'll get caught. So they swap murders."

—Bruno, Strangers on a Train

Oh, hello there. I didn't see you. I was too busy thinking about my horrible father—but you don't want to hear about it. You probably have troubles of your own. Perhaps a shrill ex-wife? And you don't want to pay her alimony anymore, you say? Well, perhaps we met for a reason. Listen: I'll "X" your ex, if you pop my pop. Ah, I knew this was a good idea. We'll each have alibis for the other crime, it's perfect. We'll never get caught.

A non-lethal version of the trope exists on sitcoms, in which two characters who can't bring themselves to tell loved ones something that will hurt them will swap duties thinking it will be less painful coming from the other character.

Examples of Strangers on a Train Plot Murder include:

Anime & Manga

Detective Conan has a filler episode in which this is used as the plot.

Fan Works

Non-murder example: In Operation P.O.W.E.R.P.U.F.F., Mojo Jojo and the Delightful Children pull this with Mojo Jojo kidnapping Numbah Three, and the Delightful Children kidnapping Ms. Keane. Mojo Jojo even points out the trope maker when he reveals the plan.

Film

Alfred Hitchcock's Strangers on a Train. It was probably Adaptation Displacement for Patricia Highsmith's book, too. Interestingly, it isn't a straight example - Guy doesn't agree to the murder swap and doesn't go through with killing Bruno's father.
Throw Momma from the Train - an homage, parody and eventual subversion of Strangers On A Train.
Horrible Bosses name-checks both the above movies. Of course, they miss the important points that they shouldn't know each other, and they should have alibis when the other murders happen.

Literature

The Trope Maker, Patricia Highsmith's novel Strangers On A Train, also isn't quite a straight example. From the start, Guy Haines explicitly refuses to be part of Charlie Bruno's plot, and leaves him to find somebody else. Unfortunately, Bruno is fond of Haines, and kills his wife anyway as a favor. Then he starts stalking Haines to try and make him follow through with his end of the "bargain". Unlike in the Hitchcock movie, Haines becomes so demoralized that he does kill Bruno's father. The plot is eventually found out by the police, in large part because Bruno ignores the "strangers" bit and starts wedging himself into Haines's personal life.
One of the Eve Dallas novels, Strangers in Death.
The Shadow Club begins as the PG version of this, with various bullied teens exchanging pranks. Then someone begins to commit more serious misdeeds, some of them dangerous, and none of them are sure who's gone too far. Everyone except the narrator did one and only one of the serious misdeeds on the unknowing behalf of one other club member they cared deeply about. The narrator winds up accepting guilt for his girlfriend's "prank," which permanently crippled a Jerk Jock.
Done in a fairly easy Clue tie-in mystery book. There are three failed attempts at murder, in each case two people with motive are missing. Since one was missing on all three occasions, the two killers are obvious.

Live Action TV

In the Castle episode "The Double Down," it was Strangers on a Boat.
- Castle even does the "criss cross" gesture. As a writer, he is understandably excited.
In the NCIS episode "The Inside Man," it was Strangers on a Commuter Train... although the crime was insider trading rather than murder, at least to start with.
- And Tony explicitly draws the connection to the Trope Namer.
- Interestingly, this one, and the above Castle incidence originally aired within the same two-week timespan, if memory serves.
In an episode of CSI, it was Strangers in a Movie Theatre (coincidentally watching Strangers on a Train).
Heartbeat. Local rogue Claude Greengrass has just been to see the movie Strangers on a Train and jokes loudly afterward about how he's like someone to burn down his old barn for the insurance money. Unfortunately, someone takes him at his word, and gets nasty when Claude doesn't keep his side of the 'bargain'.
Bones did a three way "Strangers on the Internet" version of this once.
Not to be outdone, Medium did a five way version.
Law and Order: "C.O.D." has Strangers in a Coffee Shop.
Due South does a version with one murder in Chicago and the other in Toronto.
In the Modern Family episode "Strangers on a Treadmill", Mitchell suggests to Claire that he tell Phil his jokes are rotten while she tells Cam that he shouldn't wear embarrassingly revealing bicycle pants.
An episode of Thirty Rock, has the entire cast conspire to get Liz Lemon to have a one-night stand. The episode references "Strangers on a Train" throughout.
An episode of Supertrain did a literal "Strangers on a Train" ~~rip-off~~ homage with Dick Van Dyke as the psycho.
Series two of Psychoville features a parody/homage of "Strangers on a Train." David agrees to kill Mrs Wren so that her nephew can inherit her money, with the nephew agreeing to "relieve Maureen of her pain" (she is dying of cancer) in exchange; they meet on a train to discuss the plan. It backfires when Jelly escapes with the real Mrs Wren, leading to her roommate (who was wearing a borrowed cardigan with Mrs Wren's name sewn into it) being mistaken for her and murdered by Finney, and David finding the body. Meanwhile, Maureen catches Wren's nephew breaking into her house, and kills him - then discovers he wasn't planning to murder her, he was there to give her a disabled parking badge.

Western Animation

Robot Chicken parodied this mercilessly, to the point of Crossing the Line Twice, in a sketch where O.J. Simpson is unwillingly roped into this by Roger Rabbit.
Done as part of a Hitchcock parody in The Simpsons "Treehouse of Horror XX."
Fillmore! had an episode where it looked like a vigilante was going after bullies. It turned out that the victims of various bullies had decided to fight back, but they swapped targets so that each of them would have an alibi when the bully they had reason to hate was targeted.
The final episode of the short-lived Gary And Mike, titled "Crisscross", parodied this.