Teeth Flying

One of his teeth splashed into my Kilmagoon, fifteen feet away. I fished out the tooth to keep as proof, as otherwise no-one would ever believe me.

—Cloud Atlas

It's like this: Two men are fighting, Good Old Fisticuffs. Now things get dirty. Then, one of them makes an attack to the mouth and hits. Cue the other one spitting out one tooth (or several).

This is often an Obligatory Joke with a work involving hockey players.

In funny works, this can take a humorous form: The guy who is hit will lose ALL his teeth - because they're dentures. Even if they were not hinted to be fake. Or if the work is in a setting where dentures aren't invented yet.

Examples of Teeth Flying include:

Anime and Manga

In Real Bout High School, Ryoko knocks several teeth out of the head of gang leader Takasugi's Dragon. Hey, it's his fault he was talking when the fight had already started.
Cleverly and artistically used as part of the title of Bleach chapter 426. Ichigo and Uryu both punch out the big boss of a gang who was after Ichigo, knocking out three of his incisors. The artistic part is where the chapter number appears on the teeth as they fly out. The reason why they were there? Ichigo previously had punched out seven of one of their guy's teeth.
Happens off-screen in an early episode of the Yu Yu Hakusho dub. Kuwabara is set upon by a group of thugs while he's taken a vow not to fight at all, even in his own defense. As Yusuke and Botan watch helplessly from the sidelines, Botan makes the horrified observation, "Is that a tooth?"
In Akira when Tetsuo is recaptured by the scientists Kaneda attempts to save him but a huge guard stands in his way, he attempts to fight the guard but he grabs Kaneda by the face and slams him into the ground, when he gets back up he spits out a tooth.
In Rurouni Kenshin', during Kenshin and Saito's fight at one point Kenshin hits Saito in the mouth with the blunt end of his sword and he spits out a tooth.

Comic Books

Asterix has the humorous version.
Golden Age comics tended to use this frequently.
One issue of Daredevil briefly but specifically mentions this; Daredevil lands a blow on Max the Ax that'll cost him a lot of money in dental work.
In Super Pro K.O., Prince Swagger loses two teeth after a face-first collision with a corner post.
Empowered and Anglerfish. Compare how long his teeth were before and after Emp beat him up.
Venom's teeth often go flying when Spider-Man gives him a beating. Not that it matters much, since they grow back in seconds.
- During his first fight with Tombstone he knocks out several of his teeth.
A Running Gag in the Spy Vs. Spy comics in Mad Magazine. Whenever one spy was caught in an explosion, an entire set of teeth would come flying out of the blast.
A regular event in Viz strips, especially Biffa Bacon. Biffa often loses teeth to blows from his own parents.

Biffa (in pub with father): Fatha, I bet Ten pints ye cannat knock aal me teeth oot wi' one punch.
Next panel, Father (with nine pints of beer in front of him and a tenth in his hand): Cheers son!
Biffa (toothless): Baftard!

Very common in Mortadelo Y Filemon as a result of punches to the face or explosions. For example, there is one scene where Filemon gets hit by a boxer off screen, and Mortadelo asks him if he lost a tooth. Filemon comes back into view, counting a handful of loose teeth: "No, I think I got all of them... 22, 23, 24..."
In the "Bodycount" arc of Teenage Mutant Ninja Turtles Johnny Woo Woo beats Raphael and slams him into the ground he just casually gets up and spits out a tooth.
This happened a lot in Gail Simone's original run on Birds of Prey, possibly as a way to show combat damage, and how much the fights hurt both heroines and villains alike. Huntress does this deliberately to a goon at one point, which is a bit icky, her being a heroine and all. In a subversion of Beauty Is Never Tarnished, the villain Rabbit knocks out one of Black Canary's teeth, and even proceeds to taunt her about it.
In a truly bizarre example, from Kevin Smith's take on Daredevil, the titular character knocks out two of the villain Bullseye's teeth, which Bullseye then proceeds to toss so hard they splinter Daredevil's staff. Damn!

Fan Works

In the Harry Potter/Hellraiser crossover Evil Be Thou My God, Harry is punched by Peter Pettigrew's silver hand and loses a molar in the process. He discovers this when he spits out a mouthful of blood and the wayward dentition comes with.

Film

Will Danaher does this in The Quiet Man.
Happened to Centipede in the movie version of James and the Giant Peach. Also, to the robot shark. (No fistfight, but teeth are still flying.)
This is used as a Running Gag in Undercover Blues, in which small-time criminal "Muerte" loses a tooth when attempting to mug one of the titular spies. He stalks them, determined to exact revenge, and ends up losing more teeth in most of their encounters.
Played for Drama in a scene from the director's cut of Watchmen. When Nite Owl learns from a Knot-Top that his mentor Hollis Mason was murdered by other members of that gang, he snaps and punches the man in the face repeatedly, visibly knocking a few teeth loose. The last you see of the guy is him gurgling his own blood which has most of his teeth floating around in it.
Troy: Paris manages to knock a tooth loose from Menelaus; the only good jab he gets in the fight.
In The Comebacks, Coach Fields tries to intimidate George Johnson into stepping in line, and even invites him to attack him. After being knocked down by a savage headbutt, Coach's tooth is returned to him by another player.
In Wanted when the main character snaps, quits his job and smacks his backstabbing "best friend" on the way out with his keyboard, we're treated to a Bullet Time shot of a tooth flying out, forming the second letter U to accompany the F, U, C, K and Y, O keys that flew off the keyboard. It's that kind of movie.
In the climax of Feast, the second Heroine uses a rifle butt to knock out every last one of a monster's many, many teeth. Then tops this by shoving her arm through its now-harmless jaws, and all the way down its throat, so it chokes to death!
A couple examples in Space Jam first when Yosemite Sam and Elmer Fudd shoot out Monstar Bupkis' teeth when he tries to kill Wile Coyote, when Tweety goes berserk he punches Monstar Blanko and knocks out one of his teeth, and when Monstar Nawt kicks Taz if you look carefully he knocks out a tooth.
In The Hunchback of Notre Dame, near the end, Phoebus punches one of Frollo's guards, sending most of his teeth flying from his mouth.
In Madagascar Escape 2 Africa , when Alex and the old lady are fist-fighting each other, Alex spits out his tooth and the old lady spits out her dentures.
Optimus Prime spits out what looks like a metal tooth during a fight in Transformers: Revenge of the Fallen. What a robot is doing with teeth is best left to the Wild Mass Guessing pages.
One werewolf in Dog Soldiers is kicked so hard on the mouth that one of its teeth flies into a wall and gets stuck.

Literature

Literature relating to comic books; in The Amazing Adventures of Kavalier & Clay, our heroes insist on drawing The Escapist punching teeth out of Hitler's mouth on the cover of their first comic.
The first blow of a bar fight in the Timothy Cavendish segment of Cloud Atlas knocks a tooth out of a villain's mouth and into the protagonist's drink.
Happens to Roran in Inheritance, he casually puts his tooth back in and somehow it stays there.
In A Dance With Dragons, Tyrion taunts Jorah, who responds by punching Tyrion out. Tyrion spits out a tooth and thinks, "Growing prettier every day."

Live-Action TV

Dexter ends up killing the wrong man in self defense, resulting in a temporary crown getting knocked out during the struggle, which he has to look for the next day at the crime scene before the forensics team finds it.
In the first episode of the Korean series Strong Girl Bong-soon, the title character (who possesses divinely-gifted Super Strength, slaps a gangster and very visibly sends several of his teeth flying. He reappears several times in the series, and the teeth remain missing.

Newspaper Comics

In Beetle Bailey, gags about General Halftrack losing his dentures never seem to get old.
In a Peanuts strip, Snoopy is on his doghouse with a hockey stick, when Linus comes by:

Linus: I don't believe you're a real hockey player. Prove to me you're a real hockey player!
Snoopy: (Grins widely, showing several missing teeth.)
Linus: You're a real hockey player!

Oral Tradition, Folklore, Myths and Legends

In The Iliad, Achilles did this to the Dirty Coward Thersites.
In the legend of Dietrich of Bern, Heime does this to Evil Chancellor Sibich.

Video Games

Mortal Kombat has this in the very detailed X-ray moves, which frequently involve blows to the head, with handy x-ray shots of the injury in question. Characters with non-standard skulls, like Mileena and Baraka have distinct teeth and jaws. Most of the time, teeth go flying.
Condemned has crazy hobos and homeless people. When you smack them upside the head with one of the various improvised weapons, teeth occasionally fly out and onto the ground.
Dwarf Fortress counts teeth by bunches (upper left teeth, lower front teeth, and so on), and, if struck hard enough, they all go flying. As a result of this and the AI targeting system, old forts tend to have dozens of teeth scattered all over the surface.

Web Animation

Homestar Runner was once punched in the face by Strong Bad, causing a giant tooth to fly out. However, Homestar for some reason claims that he doesn't have teeth.

Web Comics

Fin loses a tooth during Homestuck's intermission. Importantly, Diamonds sees the tooth on the floor and uses its placement to know where and when to throw a swing that, due to Fin's time powers, hits him several minutes ago, knocking the tooth onto the floor in the first place.
In Nip and Tuck, a mime chooses Tuck Todd to mock. Tuck turns around... POW!

Nip: Ouch! "Teeth Flyin' In The Wind..."
Tuck: Got a tissue? Ah got "Clown White" embedded between mah knuckles.

Western Animation

Bad guys' teeth go flying in the opening sequence to The Powerpuff Girls. And one episode of The Powerpuff Girls was pretty much based on this trope - Buttercup learns the Tooth Fairy gives you money for teeth, and starts deliberately knocking villains' teeth out and collecting them to make a huge windfall.
In the "Pecos Bill" segment of Melody Time, Bill knocks out all the gold fillings off a gang of rustlers, which is why "there's gold in them thar hills".
In the SpongeBob SquarePants episode where SpongeBob has to impersonate Mr. Krabs at his Navy reunion, one of Krab's buddies asks to punch him in the "armor abs", resulting in one of his teeth coming loose. The others are disappointed that he only lost one tooth, until he spits out a few more and then his skeleton, and the others declare, "Now that's manly!"
At the end of The Little Mermaid, Louis the chef loses a few teeth after getting hit on the face by a mast.
- Happens to Morgana's pet tiger shark Undertow near the end of the sequel after accidentally hitting a wall and is presumably killed. Since sharks inevitably grow their teeth back immediately if they all were to fall out of their mouths, it's possible that Undertow may have actually survived.
In Batman: Mask of the Phantasm during Batman and Joker's fight at one point Joker smashes a model building over Batman's back then attempts to stab him with the point, in response Batman kicks him in the face knocking out one of his teeth.
In the American Dad episode "Haylias" when Hayley has gone insane after activating her chip she attempts to kill Stan at one point she punches him in the jaw knocking out a tooth, and we get a close up of the bloody tooth flying from his mouth.
A recurring gag in golden age cartoons like Looney Tunes and Tom and Jerry when a character receives a blow to the face their teeth will often shatter like glass.
Basically anytime there is a fight scene or when someone receives a blow to the face in Ren and Stimpy teeth usually fly from their mouths.
In The Boondocks episode "Grandad's Fight" during Robert's fight with Stinkmeaner he knocks out all of his teeth.
"Boy, I was a fool in school for cutting gym!"

Real Life

A common saying in whitewater rafting explaining the reason that you keep a hand on the end of your paddle at all times (to avoid the hard plastic end from smacking someone in the teeth) is that you'll end up with "summer teeth" as in, "Sum'r in the boat, Sum'r in the water, and if you're lucky, Sum'r still in your mouth."