Blast Out

""Oh, well -- Plan B. Let's just kill each other.""

- Castor Troy, Face Off

Someone pulled a trigger in an unstable situation. Everyone starts blasting. For this trope to work right, the outcome has to be truly up for grabs. Usually happens in a Mexican Standoff.

One possible result of the Powder Keg Crowd. If this happens at the finale of the story, often results in a Bolivian Army Ending.

Anime & Manga

 * The grande finale of Ranma ½ has Soun Tendo attempting to force Ranma Saotome and Akane Tendo to be married at last, having stolen a cure for Ranma's Gender Bender curse that was sent to the dojo as a reward for Ranma's attempts to save Jusenkyo and intending to blackmail Ranma and possibly Akane into going along with the wedding. Ranma promptly abandons Akane at the altar to try and steal the cask of Nanniichuan back, his other fiancees show up and start slinging explosives around to prevent the wedding, and his father, Ryoga and Mousse all show up to try and take the Nanniichuan for themselves. How does it end? The reception (both the party and the hall) has been blown to hell and back, and Happosai's drunk the Nanniichuan water. Nobody gets married, cured, or makes any serious attempt towards sorting out the Love Dodecahedron.
 * In one episode of Project A-ko, the entire clientele of the alien warship-turned-restaurant turns out to be agents from different special intelligence agencies. This naturally results in a massive free-for-all brawl and shootout.

Film
"Hicox: "There's just one thing left to do." Maj. Dieter Hellstrom: "What's that?" Hicox: "Stiglitz?" Sgt. Hugo Stiglitz: "Say auf wiedersehen to your worthless Nazi balls!""
 * The ending of Reservoir Dogs. Mr Orange, Mr White, Nice Guy Eddie and Joe Cabot are pointing guns and yelling at each other and then it's over very quickly.
 * The climax of City on Fire, a 1987 Hong Kong film that influenced Reservoir Dogs.
 * The ending of The Wild Bunch. A literal Mexican Standoff between The Bunch and The Mexican Army ends with everybody(women, children, livestock, etc.) getting killed in a hail of bullets, complete with a heavy machine gun blazing.
 * The end of the Will Smith movie Enemy of the State, in which Will Smith hides under a table during a Mexican Standoff. It devolves into a Blast Out between the Mafia and the evil government agents, and nearly everybody dies.
 * The movie Desperado, where the main character gets into a Blast Out with an entire bar full of Mexican gangsters and somehow manages to survive. We never even see how he manages to survive a shoot-out with an entire casa full of goons!
 * Pirates of the Caribbean: At World's End, Jack pulls the trigger during a Mexican Standoff, but it turns out the powder in all their guns is wet, so none of them go off.
 * True Romance.
 * The movie Tombstone portrays the Gunfight at the O.K. Corral as a tense standoff before a sly wink from Doc Holiday to Billy Clanton turns it into a full blown Blast Out.
 * In the film version of Children of Men,
 * The Til Schweiger movie Eisbär (Ice Bear) from 1998 has many references to Pulp Fiction, but it ends in a Mexican stand-off (only with Europeans). It culminates in a very impressively staged Blast Out.
 * Battle Royale has this as one of the most memorable scenes in the film: A group of about 10 schoolgirls are sitting around a table, in a refuge from the senseless slaughter around them. Then someone gets poisoned. Someone else gets paranoid, picks up a gun, and starts shooting. Everyone else follows suit. Survivors: 0. Time elapsed from happy to everyone being dead: 2 minutes, 17 seconds.
 * Inglourious Basterds:


 * In Lock, Stock and Two Smoking Barrels, the gangs of Rory Breaker and Dog stumble upon each other with guns drawn, both expecting to find someone else. They start shooting anyway.
 * Parodied in Facepunch!, a fictional movie in the film adaptation of New Moon. The only audio we hear consists of a standoff quickly falling apart. LET'S DO THIS!
 * Double subverted in Saving Private Ryan, during one scene an American soldier accidentally knocks down a wall by leaning on a log, only to reveal a squad of Germans on the other side, both the Americans and Germans scream and point weapons at each other, and right when the viewer thinks both sides will start firing...
 * In Peter Jackson's adaptation of The Two Towers, Saruman's forces reach Helm's Deep and there is a tense moment while the Uruk-hai pound their spears on the ground. and the defenders prepare to fire. Suddenly an old Rohan man loses his grip on his string and lands one in an Uruk-hai neck. After a moment of stunned silence, the battle begins.
 * In Basic, this occurs several times

Live Action TV

 * Invoked in an episode of Burn Notice, when the Villain of the Week is tricked by Michael and his friends into thinking that one of his henchmen is a traitor. This later results in a Mexican Standoff/argument between the villain, the "traitor", and some Mook who has no idea what the hell is going on. Sam, who is outside posing as a corrupt cop (long story), then fires his gun into the ground and then we hear a few off-screen shots, the villain begging for his life, and then one final shot. Michael even lampshades this when he says that arguments with guns drawn are not a good idea since everyone is tense and anything could set it off.

Mythology

 * Possible Older Than Print ur-example: The Battle of Camlann in Arthurian legend is said to have begun when, at a tense parley, a soldier drew his sword to kill a snake.

Video Games

 * One Mexican Standoff between four Mah Jhong players in Killer7 winds up with all four men pulling the triggers simultaneously and all dying at once.
 * How  meets his end in Red Dead Redemption.
 * This trope determines who has the starting advantage during some of the multiplayer game types while the players who were killed during it have to wait until they respawn.

Web Original

 * One of the best examples of this in Survival of the Fittest is the Mexican Standoff between David Jackson, Jacob Starr, and Peri Barclay. To cut a long story short, Jacob snaps and starts shooting and a large fight ensues. Remarkably, very few people were injured.

Western Animation

 * Parodied in the Huck Finn episode of the Simpsons, a saloon undergoes a blast out when everyone pulls derringers out from a variety of hiding places, including from within the barrel of a larger gun, and starts firng wildly... and they are revealed to be unable to even damage glass. "These derringers sure are weak, Tom." "Powerful weak." One bounces off someone's eyeball, not even causing them to blink.