Kakuzu of Naruto has most of his joints modified by his kinjutsu to come apart at will; this results in disturbing Glasgow Grin-like disfiguration of his face. While in the four-tails form, Naruto also displayed this, though it healed after.
After injecting himself with Orochimaru's genes, Kabuto has a new snakelike form. In this form, he can open his mouth so wide it practically rips open. This results in clear cut marks on the sides of his mouth even when it's closed.
Heinkel from Hellsing gets one of these toward the end after taking a sniper round through the mouth. She doesn't seem too bothered by it, but it makes her dialogue a nightmare to read.
Joejoe of Toriko has what looks like stitches on the entire length of his mouth, which runs for the entire width of his visible face. Zebra has half of a Glasgow Grin—his left cheek is torn, exposing his teeth up to the wisdom ones. It might be intentional—he claims it's useful for shoveling food in, and might be possibly useful for all his shout-based attacks. For a short time, Zebra's cheek was sewn together, but the stitches gave way quickly.
Doctor Hogback in One Piece has stitches that extend beyond his permanent smile to encircle his whole face. It fits right in with his expertise of Frankensteinian assembly of corpses via stitching. Despite this smile, Hogback can express a full range of emotions via body language.
The Comedian in Watchmen has half a Glasgow grin, after being slashed by a Vietnamese woman whom he'd gotten pregnant.
Though not typical, some artists do depict The Joker this way, particularly in out-of-continuity stories such as Brian Azzarello's Joker graphic novel.
The Batman Confidential story arc Lovers and Madmen, a re-telling of the Joker's origin, had the Joker given his Glasgow Smile by a thrown Batarang.
On a similar note, the Joker's Earth-3 counterpart, the Jokester, did have one of these from his encounter with Owlman I and Talon.
The Ame-Comi Girls universe's version of Duela Dent, the Joker's Daughter, received such scars after being attacked by dozens of bats.
Mr Rictus from Wanted has this, though it's due to horrible burns rather than cutting.
The Green Lantern series has Karu-Sil of the Sinestro Corps, a Wild Child who cut off her lips and sharpened her teeth into fangs so she could look more like the large beasts that adopted her, giving her a permanent predatory grin.
In The Dark Knight, the Joker has had his mouth cut open at the corners in lieu of the character's traditional rictus grin. The origin of these scars is left "unknown". During the movie he appears to give one to Gambol.
Which, interestingly enough, brings the chain of references full-circle: The comicbook Joker's rictus grin was based off Gwynplaine from the film version of The Man Who Laughs—who had a Glasgow Smile in the original novel.
The Bride gives one to a hapless Mook during her battle with the Crazy 88. Compared to some of the other wounds she inflicted, it's hardly the worst way to go.
One of the most fearless of the Dead Rabbit warriors in Martin Scorsese's Gangs of New York is a large Irishman named Jack Mulraney whose left cheek is curved up in a permanent grin thanks to a long-ago knife injury. Because of this peculiarity, the other gang members call him "Happy Jack."
Kakihara (from Ichi the Killer) sports one. Except it hasn't healed and is held together with rings at the corners of his lips.
In Saw 6, Detective Hoffman gets half of one of these as he barely escapes a reverse beartrap with his jaw intact. There is a scene in the seventh movie where he stitches his torn cheek shut.
The original film example is The Man Who Laughs, whose face was permanently deformed into a grin as a punishment for his father's misdeeds.
I Saw the Devil has a horrifying variation, wherein one of the cannibals gets "A permanent smiley face" by having his lower jaw pulled until his cheeks begin to split.
Godzilla has a "born with it" variation in Godzilla (2014), though it's only really visible when he opens his mouth to roar or use his atomic breath. Its design seems to be based off the similar "smiles" of many real life reptiles.
Mr. Grin from Stormbreaker is a former circus performer who used to catch a knife between his teeth as the finale of his act, until his mother came to see his act and distracted him at the crucial moment. In addition to the scars on his cheeks, he has no tongue.
The title character of The Man Who Laughs, by Victor Hugo. Despite having this trope, he isn't that bad.
In the Discworld novels, author Terry Pratchett plays with this when he writes about Death, who carries the personage of The Grim Reaper. "Death grinned" is a frequently-used description, averting mention of the fact that he never stops grinning, being a skeleton in a robe.
Early in Fight Club the protagonist gets a hole punched in his cheek, which he covers with two fingers when he drinks coffee. Later he tries to commit suicide by fighting fifty guys, splitting the cheek completely. The he shoots out the other cheek. He points out that he now looks like a piece of vandalism from earlier in the book.
Katniss from The Hunger Games would've gotten one if Thresh hadn't stepped in when he did.
In Joanne Harris's Peaches for Monsieur le Curé, Inès Bencharki turns out to have one of these.
Vestara from Fate of the Jedi has a deformity near her mouth that gives her the appearance that she is smirking. The fact that it resembles a smirk is also the only reason the Lost Tribe of the Sith let her live (as they don't want their members to have birth defects).
Mentioned in "Journal of a UFO Investigator" by David Halperin. The MIB discuss to cut the protagonist one "so he looks better". (At least that he is spared.)
The Rifter: Kyle has the "Glasgow smile" scar. He was a supposedly celibate initiate at a monastery; the senior priest Dayyid cut him as a mark of shame after catching him with a man in an alley. Dayyid needed him to become the Kahlil and so couldn’t have him publicly accused of homosexuality and executed, but everyone in Rathal’pesha knew what the scar meant and he was utterly ostracised.
In Alex Grecian's The Black Country, the "gray-eyed American" has a huge gash in his face from his lip up through the cheek, courtesy of Calvin Campbell.
Young Bond novel Blood Fever has a fellow named Smiler, who is Count Carnifex's head henchman and assassin. He got his name from the scars that he bears on his cheeks, which he received for betraying his last gang. In Glasgow.
Legends and Mythology
Kuchisake-Onna, a woman in Japanese legend, wanders around wearing a mask over her slashed ear-to-ear mouth and asking people whether she's beautiful. What happens after this varies, but it always includes the threat of her slitting your cheeks like hers, whether you say "yes" or "no" (the word she uses for "pretty" is a homophone of the verb form of "cut", which is why she will attack you if you say yes). Some versions also give her More Teeth than the Osmond Family on top of it, just to up the creepiness factor. However, there are several third options for dealing with her, such as apologizing that you have to be somewhere else right now or saying you're neutral or ambivalent on her appearance.
On Dollhouse, Alpha gives one to Victor, though it later heals.
In season 3 of Nip/Tuck, this is the identifying mark of victims of The Carver.
You can choose a Glasgow Smile for your character in Brink, and, just like in real life, it's permanent.
Kefka Palazzo in Dissidia sports a Glasgow grin with his redesign for the Dissidia subseries of the Final Fantasy series, both the Heath Ledger's Joker variation (normal form) and the more traditional variation (EX-mode)
Croagunk, Toxicroak and Scraggy from Pokémon. Scraggy loses the Glasgow Grin upon evolution, however.
He had a similar, but less noticeable example in the ending of Metal Gear Solid 4. The reason is, before the fourth game began, Raiden's body was replaced by an artificial cyborg version, leaving only his head sans lower jaw intact. That line is where his organic parts connect the cybernetic parts.
The very first episode of Batman Beyond features a Joker pulling a huge knife on Terry and declaring his intention to "put a smile on his face". This is probably something Jokers do a lot.
Character actor Tommy Flanagan (who was in Braveheart and Gladiator, among other things) has what a healed Glasgow Smile really looks like, having received one after being jumped outside a bar. Also, Tommy Flanagan is from Glasgow. His most frequent role is as Chibs in the series Sons of Anarchy, where his scar is part of the plot.
The body of Elizabeth Shortnote better known as "The Black Dahlia" was found with a Glasgow Grin carved into her face. (Don't go looking for pictures unless you have a strong stomach; it is disturbingly easy to find incredibly gruesome crime scene photos of Short.)
David Faber, a Holocaust survivor, once visited a school and calmly told an auditorium of middle schoolers how his Nazi interrogators put a vice inside his brother Romek's mouth and proceeded to slowly crank it open until Romek's jaw broke and his cheeks tore open. All this to get information from David, who knew nothing about what they were asking him about.
UFC featherweight champion José Aldo received a partial one in a childhood accident. Though long healed, the scar is easily noticeable.
Union general William Rosencrans of the American Civil War had been injured badly in a fire; he got reconstructive surgery on his face that left him looking like he was permanently smirking.
A common myth among Portuguese school students is the existence of a gang called "Clown Face". If they catch you, they give you a choice: death, rape, or clown-face. The first two are Exactly What It Says on the Tin, and you can guess what the last one is.