In the animal kingdom, baring your teeth is a sign of aggression. In the case of humans — well, there's something very disconcerting about a smile that doesn't have an ounce of happiness in it. It's downright frightening when the smile is in anticipation of pain or death — yours, probably. Needless to say, the Slasher Smile does not inspire warmth in anyone who sees it.
The Slasher Smile is the evil sibling of the Cheshire Cat Grin. In general, the difference is in the eyes of the character. If the eyes sparkle, or are mischievously wicked, it's a Cheshire Cat Grin. If, however, the eyes are clearly crazy or malevolent, it's a Slasher Smile. If the grinning person is holding a knife or an axe or some other implement of painful and often bloody death, it's best to assume the worst.
While the Cheshire Cat Grin is a staple of The Trickster, generally one of the good guys, the Slasher Smile is the staple of the Ax-Crazy, unless said hero is a particularly dark or vicious Anti-Hero. Only expect to see a "nice" hero with a Slasher Smile if they've been possessed or suffered a major Freak Out! or if they have been taken over by their Super-Powered Evil Side. Also, a devious Chessmaster or Magnificent Bastard is unlikely to look like this - it's too Obviously Evil, and they prefer the subtler Psychotic Smirk.
No, the Slasher Smile is more appropriate for The Dragon, the Mad Scientist, and most especially Serial Killers, but it can happen with any character who is gleefully violent and/or fits any "wild crazy person" stereotypes. Beings who hunt and eat victims we are supposed to identify with will also often have Slasher Smiles... in their case, it means "Hello, lunch!"
Some characters with a Slasher Smile wear the grin all the time — in fact, it's physically impossible for them to move their face out of it. For many, this has the added worry of making it harder to tell what they're thinking or feeling, because their face betrays no expression beyond the smile.
Not to be confused with aSlashed Smile (although they sometimes overlap), and has nothing to do with the pleased smiles of Slash Fic fans upon the detection of impending Ho Yay. Hopefully.
Contrast Dissonant Serenity for a calm mood which isn't the slightest bit more reassuring. When the smile is merely creepy, it's The Un-Smile. May be part of the fear behind the Monster Clown. See also Technically a Smile. Also contrast Grin of Audacity.
Dr. Hell from Mazinger Z and Great Mazinger never smiled. He GRINNED (usually when he thought he was winning or believed he had won. Or simply when he felt people were frightened of him). And it was deeply disturbing. It was even creepier in Mazinkaiser.
Tetsuya Tsurugi, The Hero from Great Mazinger, was a Broken Ace usually wore a grim, angry or bitter expression. But when he grinned in battle, it was very eerie.
Xellos from Slayers has this in spades. It's less common to see him not smiling than to see him with a smile (or a convenient Psychotic Smirk) on his lips, but if he's smiling and his eyes are open, you're in serious trouble. Especially exemplified as he's sadistically torturing Valgaav in TRY and a highly amused smile never leaves Xellos' face, backed up by a truly psychotic giggle.
This is used to identify characters who fight for the love or madness of fighting rather than higher ideals, such as with Kenpachi, Ichigo's inner hollow, Ikkaku, Nnoitra, Ginjou, and Unohana. Ichigo sports one in battle sometimes as well.
This is used to identify scientists unleashing their chance to experiment on others For Science! or reveal any bizarre inventions they have created. This tends to be as much a problem for their allies as for their enemies. Examples include Mayuri and Szayel.
It is used to identify creepy characters who cannot be trusted and are hiding ulterior motives, such as Gin.
It is used to emphasise a character on the battlefield is unhinged and descending into insanity, such as with Tsukishima and Nianzol.
Greed, both his first body and in Ling's, have this. Pride's shadows also usually have this default expression as does his body after he eats Gluttony. Must be a family trait since Father was shown to have one back in the days where he was only a blob in a flask and he can still pull it off as shown When he leaves his 'human form' which is just a humanoid blob with these and eyes.
Barry the Chopper has one built into his helmet.
Some of the minor characters even have these, such as General Raven, when he's trying to offer someone immortality and in his Eye Catch, and also some of the more unsympathetic State Alchemists that participated in the war.
Truth almost always has this expression on his face, because he's a sadistic dick who enjoys handing out ironic but disproportionate punishments to people who try to break the laws of the universe. The only exception is when Ed correctly offers to sacrifice all of his alchemist powers to get Alphonse back, Truth displays a real happy smile as he cheerfully congratulates Ed on choosing the right answer and opens the way for him to retrieve Al and dissolves into nothingness.
Gluttony adopts a slasher smile after Dante destroys his vestiges of humanity in the 2003 anime.
Also in the 2003 series, Lust adopts an eerie one when she attacks Scar in the 18th episode.
Anti-Hero example and a subversion: Revy from Black Lagoon routinely wears this kind of grin when she's busy gunning down bad guys, particularly during the first major shootout of the series, where Rock sees her smile for the first time and is extremely creeped out. However, that's just Revy on a normal day. What you really want to watch out for is when she drops the grin and goes all emotionless and monotone, because that's when she stops pointing her guns at the bad guys and starts pointing them at everyone.
In the manga arc El Baile De La Muerte, Roberta, as her sanity continues to spiral downward into Ax Crazyville, starts sporting these. And so came the time when she snapped one of Shenhua's throwing knives, WITH HER TEETH, while wearing THE Slasher Smile. Bad Ass.
Creepy Twins Hansel and Gretel take this trope to a ridiculous level. Think vampires.
Balalaika's a kid in a candy store during the "Fujiyama Gangster Paradise" Arc. She's ordering hits, snapping necks, and holding a gun to Rock's head with that huge grin.
And intentional. Considering he's not even an antihero, the psychological warfare aspect is neat.
Accelerator is always seen with an evil smile when he is enjoying a good fight or a massacre, maybe because his awesome powers makes many times the fights boring, for example when an army tried to beat him, when the Misaka sisters tried to fight him and one the most boring "fights" he had was when Mikoto Misaka tried to attack him, he really looked bored.
Agito of Air Gear. He has this whole shark fang thing going on.
Yomi from Ga-Rei puts one on when she's under control of the Sesshouseki. It's even creepier when her eye colour inverts.
Osaka's attempt to "wake up" Yukari in Azumanga Daioh fell into this from a different angle. Osaka always looks a bit blank, and she was half-asleep when she tried it... which just resulted in her standing in the doorway with a blank, empty smile and a large knife. She had no violent intentions, but she sure looked like someone was gonna get stabbed.
Probably her. Earlier in the episode she expressed a lifelong dream of waking someone by banging a ladle on a pan next to their ear. The only thing keeping Osaka from cutting off her own hand was Yukari woke up when Osaka opened the door.
A slightly more trope-y Slasher Smile (more of a Slasher Smirk) is here, at about 0:40.
There's been a few characters who do this in Fairy Tail, but the crown for the most disturbing Slasher Smile goes to an all-around psychopath named Jackal, a member of Tartarus, which he sports while slaughtering the Magic Council, as well as forcing a Sadistic Choice on Lucy involving her choosing whether to save the life of a former Magic Councilor... or a pregnant woman, who was crying and trying to reassure her unborn child that everything would be okay. Yes, the Tartarus arc took the Darker and Edgier level of this series Up to Eleven like never before.
Though a machine manages to give him a good run for his money.The arc's Doomsday Device,Face,a large pillar with,well a face on top,looked kinda stoic when we first see it.It turns out there's more though,and we see some with...rather creepy smiles on them.
Kaguro from Kekkaishi almost constantly has one of these, and an endless supply of lethal blades to back it up.
Eva Unit 01's really deserves special notice, because in that picture it's smiling after having already been brought back into the hangar after the fight with Zeruel. The fight in which it ate Zeruel alive to absorb it's source of unlimited motive power and tore off NERV's restraints, and in doing so completely removed NERV's ability to control it. Past that point the only reason NERV can keep it in the hangar at all is because it's letting them keep it there, and the soul inside is grinning with the knowledge that it's now become literally unstoppable.
Even Shinji shows a couple, most of them during the battle with Zeruel.
Some people regard Rei's rare smiles this way as well.
Fruits Basket: Hatsuharu Sohma's Split Personality, Black Haru, has some pretty disturbing smiles that are nonetheless better than the alternative (in the vein of "I'm going to love kicking your ass" is better than "I'm going to kill you").
Death Note: As L dies, before he closes his eyes he sees Light looking at him with one of these. Higuchi, too, after getting the Shinigami Eyes. One look at that creepy face and death will follow, without the Death Note.
Light again, during the finale (at least in the manga), sports one so big he gets cross-eyed.
Mikami Teru, one of the most psychotic of the Kiras, also sports one of these on occasion.
The Death God Ryuk also has one permanently etched to his face, along with More Teeth than the Osmond Family. Light showed what a badass he is when he only was seriously freaked out for a few seconds, when Ryuk spontaneously appeared in his bedroom.
Sasuke wears one before stabbing through Karin to get Danzo. RUN. He makes quite a few other ones after that, up until Naruto tells him they'll both die if they fight after which he goes back to a more focused look.
Chapter 574: Sasuke shows another. And it is creepy. Just look.
And here's another exemplary performance from Gaara.
This is Orochimaru's and Hidan's default expression.
Zetsu seems to have this whenever he's battling someone.
Also, Dark Naruto has this as his default expression.
Kisame. The only times it usually leaves his face is when he's using a jutsu and has to expel water from his mouth.
Kabuto gains one after he absorbs Orochimaru's DNA.
Sakura gets one in a comedic fashion after Konohamaru insults her.
The normally-stoic Madara Uchiha instantly develops an epic◊ one when he feels the First Hokage's chakra. Between him, Sasuke, and Itachi, it looks like terrifying expressions are just another part of the Big Screwed-Up Family. Sadly, the upcoming anime version, seen in the opening credits of Shippuden episode 357, does not do his slasher smile justice. The manga is far creepier..
I stand corrected: the actual anime episodes version does do it justice! WOW!
Which now includes the Fourteenth, which is downright disturbing considering his host is Allen Walker. Seriously, who expected the kid to ever look like this?
And now Allen doesn't even need the 14th Noah to do this. Somehow, he manages to make such smiles even worse.
And the when the Earl is pissed off, the preexisting smile goes so far off the deep end that hiding under the bed begins to seem like a very attractive option. Meep?
For someone who doesn't smile very often (or only smirks), Kanda seems just too creepishly happy when the room collapses on him and everything turns into empty space in the Ark. When he comes back, he starts his day by arguing with Allen rather than thinking about how he could've died.
Road Kamelot does this sometimes as well too, especially when she starts to get too much fun out of tormenting the main characters.
Another one, coming from Force, is Cypha of Huckebein. The number of times her smiles weren't this kind could be counted on one hand... if there were any to count. The only other expressions she exhibits are either stoicism or being scared shitless from underestimating her opponent.
Riful from Claymore shows one when she first encounters the Abyss Feeders. Made creepier by the fact that there's a large bite out of her head.
Ophelia wears one as her usual facial expression because, well, she's what happens when you give The Ophelia a BFS.
Warsman, from Kinnikuman, is a cyborg. Predictably, he normally can't smile... unless he's in his batshit psychotic personality, in which case he sports the Warsman Smile. He did use it once, while normal, to catch an arrow in his mouth, though.
With Getter Robo, it'd be easier to list the characters who don't have one of these plastered on their faces most of the time. Ryoma in particular seems to have this as his natural expression.
Donquixote Doflamingo has this as his default look, appropriate for what seems to be One Piece's counterpart to The Joker.
Eustass Kidd sports one almost all the time, Funnily enough, his face even looks quite similar to the Joker, but even he isn't quite as psychotic as Doflamingo.
Blackbeard has had a few.
This happens to the Straw Hats (minus Luffy and Nami) when Oars has his horns stuck to the ground and unable to move. Cue the Straw Hats' slasher smiles and a nonchalant, epic, off-screen beatdown of Oars.
Much like the Oars example, Luffy, Robin and Zoro get slasher smiles (and Glowing Eyes of Doom in the anime) when they reach the cold side of Punk Hazard and see centaurs wearing warm clothes.
Creepy Child Sugar gets one of these in Chapter 758 when she goes after Luffy.
Vinland Saga: Thorfinn, when he does smile. Thorkell's is more of a Slasher Grin, with a big thumbs up thrown in there.
Neuro has a psychotic grin most of the time, and then he reverts to a parrot-headed-Eldritch Abomination. There's also the twisted, insane looks of the criminals as they confess.
Grelle Sutcliffe the Shinigami from Kuroshitsuji has one of these. Made even better and creepier by the fact she had just finished murdering someone a few seconds ago and is covered from head to toe in blood. Too bad it isn't really seen again after this, because she's too busy being a goofball, playing with safety scissors. Yes, really.
Yami Bakura often has one as well, even moreso during the final arc.
Not so much in the anime, but during the Death-T arc in the manga both Kaiba brothers each get a couple at the prospect of killing Yugi and his friends.
Seto actually sports one a lot in the manga, especially when he's about to crush an opponent during a duel.
Dartz gets one when he uses the Seal of Orichalcos in the final battle against Yami Yugi and Kaiba.
In the early chapters of the manga when Yami Yugi's character was a lot darker and you weren't really sure if he was truly a good guy or not, he almost always sported one... especially when he declared to a rival that they would undergo a "penalty game" if they lost to him.
Also from GX, Saiou/Sartorious at first only sports a Psychotic Smirk but graduates to this as a sign that he has been completely taken over by The Light.
As a Neat Freak, Ryuuji from Toradora! gets one whenever he cleans. As in, dirt and dust and mold. Combined with his permanent death glare, he looks like he's rejoicing in the thought of committing genocide on entire societies of dust mites and mold colonies. There's a brief shot of one right in the opening theme.
Hiruma Youichi from Eyeshield 21 has one of these, aided by his fang-like teeth and his habit of constantly carrying large guns when not on the field. In fact, he does it so often that he scares his teammates when he DOESN'T have a slasher smile, and uses it to his advantage against his opponents.
Lelouch right after he successfully orders a collective suicide with his handy-dandy new geass. Being onlysemi-crazy, he otherwise reserves it only for special occasions (such as having just added another few digits to his kill count).
This is also the apparent default expression for any Geass thralls ordered to kill someone. Including themselves.
V.V. has one during most of the time he's piloting the Siegfried against the Black Knights during their attack on the Geass Order.
Captain Ginyu breaks into one right before he uses his body change ability to switch bodies with Goku.
In the filler "Garlic Jr. arc" in Dragon Ball Z, when Piccolo is infected with the Black Water Mist and turned evil the first thing he does to let us know this to break into one of these smiles. Turns out he's actually faking being infected though.
Vegeta gets one after getting possessed by Babidi and becoming Majin Vegeta◊.
Even before that, he sports one◊ after he kills Jeice.
Super Buu and Kid Buu smile like this by default since they're both textbook definitions of Ax-Crazy characters (or forms in this case). Frieza occasionally breaks out this smile too, a good example being when he shot Piccolo through the chest with his death beam.
One episode of Kyou No Go No Ni mentions how nobody remembers seeing Emotionless Girl Kazumi Aihara ever smile. If the first episode is any indication, it's because her smiles end up as one of these...
In Monster, the unspeakably evil Johan Liebert, commits Mind Rape on a former cop who had killed a boy while drunk and is trying to atone, playing on his guilts. He eventually asks him how he would look his estranged daughter in the eyes and then realizes that he's got him, and then makes one of the most unsettling and terrifying smiles imaginable before asking "well Richard, how about a drink?"
Speaking of Gundam, Desil Galette from Mobile Suit Gundam Age sports a horrific one when he casts off his cute child persona at the end of Episode 13. Seriously, you wouldn't imagine a seven year old to look like this,◊ would you?
The first episode of Persona 4 has Yu with a (completely heroic and yet still disturbing) slasher smile on his face while summoning Izanagi for the first time.
In the 10th episode of Phantom ~Requiem for the Phantom, when Reiji begins chasing after Scythe Master, he starts breaking into this◊ twisted grin. Combined with his creepy laughing and this little piece playing in the background and the whole thing easily goes into Nightmare Fuel territory.
Akura-ou from Kamisama Kiss, being a Psychopathic Manchild, has this as his default facial expression. One of the main protagonists, Tomoe, also tends to sport one when he is about to do something nasty. Small surprise since he used to be Akura-ou's partner in crime.
Mahiro Fuwa in Zetsuen no Tempest seems to have an emotional spectrum that ranges from 'indifferent' to this◊. Frighteningly enough, he's regarded as far less of a threat than his best friend.
Tsuchiya gets one in Holyland chapter 144 just before he turns a fight around.
In Attack on Titan, Annie smiles like this when she is correctly accused of being the Female Titan. Made even creepier since this is the only smile (or any other expression other than indifference) she's given so far in the series.
This is also the default expression for some of the titans due to the way the skin on their faces has stretched.
Armin of all characters, pulls one while lying to Bertholt about how Annie is being subjected to torture. It's actually kind of jarring.
In chapter 51, Erwin sports one after finding out that titans were once humans. It was so unnerving that even Levi was disturbed by it.
Armin also pulls one of these in the second OVA when Jean suggests stealing meat from the commander's office. Makes you wonder how far off the deep end he truly is, doesn't it?
Just about everyone in Drifters. It could even be said the heroes do it more than the villains.
Kunitoshi Joukyuu, the protagonist of AIKI, loves using these.
The literary example, The Man Who Laughs by Victor Hugo, which is commonly cited as inspiration for The Joker, involves a man whose face is horribly mutilated so that he cannot stop smiling and how his psyche is twisted by this. In order to maintain the grin throughout the movie, actor Conrad Veidt had to get metal hooks in his mouth to pull back his cheeks. Nevertheless, the character is a really nice guy.
In Frank Miller's All Star Batman, the Dark Knight himself has one in both his costumed and civilian identity, especially when thinking about his young ward, age 12. Squick.
The Juggernaut enjoys his role as an unstoppable engine of destruction.
Johnny of Johnny the Homicidal Maniac would usually have one while torturing or killing victims. Mr. Eff and Psychodoughboy had permanent ones because Johnny painted them onto their faces.
Judge Death does this all the time as well. Mostly because his lips have rotted off.
In Spider-Man, Carnage's alter ego Cletus Kasady has one of these.
In fact, symbiotes appear to have some sort of demonic smile on their faces sometimes.
In the classic Spider-Man vs. Wolverine, there's a scene where they're duking it out in an East German graveyard. Spider-Man thinks, "I'm hitting him hard enough to wreck cars... and I can't get him to stop smiling..."
Mystique in the "Wolverine" story arc "Get Mystique"; just before their final climactic confrontation she strips naked, festoons herself with weapons, puts on a slasher smile and says, "Coma and GET me, Lover!"
Wonder Woman villain Doctor Poison has a big creepy smile, pulled up by metal hooks she slips into the corners of her own mouth.
The Corinthian has three: he has devouring mouths instead of eyes behind his shades. Fitting, since he's the eidolon (the word eidolon being especially apt here: it connects strongly to concepts such as delusion, idol, spirit, or bogeyman) or archetype dream that inspires and is inspired by Serial Killers.
One of the last things you want to see is Ultimate Hawkeye covered in the blood of the squad you sent to subdue him, holding their weapons and grinning into your security camera telling you, "Run", when you are part of the group responsible for his family's murder. Unfortunately for you, it is the one of the last things you're going to see.
Bullseye.◊ Yeah, you see that space where he's missing a tooth? That's cause he killed a guy with it.
Subverted in an issue of G.I. Joe. Formerly masked gunmen hold a family hostage in a remote house with the result being the authorities are not sure at first who are the hostages and who are the hostage-takers. One of them seems to be grinning maliciously all the time and the footage they have of the masked rampage shows them all grinning like maniacs while gunning down innocent people. So obviously the one with the constant grin is one of the bad guys? Wrong, he's the father of the innocent family caught in the middle, and a veteran who had suffered permanent damage to his facial muscles during active military service.
Kid Miracleman from the series of the same name is constantly depicted with this facial expression. The scariest example is probably from the cover of Issue #15 (which can be found in the Image Links)- truly horrifying just from the sheer inhumanity of that grin.
Grimjack sports one whenever he is in a fight. The smile is an involuntary tick that he developed as a child gladiator where he was known as "The Grinner." Also, combat is the only time you ever see him smiling.
Let's Do The Caramelldansen has the most brilliant description ever. "So Vexen smiled, and it was... a purely evil smile. A MANIACLY evil smile. Take every synonym for 'evil', put them before the word 'smile', and you may even get Vexen's smile. It's hard to comprehend how truly terrifying the smile was. But if Hitler and Big Brother had a child, and that child had a child with Satan, and that child had a child with the child of Voldemort and Darth Vader, and that child were to smile, it would probably the closest you could get to how awfully evil Vexen looked at that moment. (Sorry for that image, people) It could make a serial killer cry." That is how the smile was described, scary huh?
When the killer Drew is revealed in the Hannah Montana story I Didn't Sign Up For This, the first thing she does is shoot heraccomplice with what is described as "a creepy smile" on her face.
Ursula of The Little Mermaid does this a few times during the final battle. Her alter-ego Vanessa even pulls one off when she throws a pin at a mirror with enough force to knock it back while gloating about her inevitable victory.
Gaston sports one at the start of his fight with the Beast in Beauty and the Beast. And yet another after stabbing the Beast in the side.
In Ratatouille, Colette's opening Knife Nut sequence to her mentorship of Linguini (and, unknown to her, Remy) is especially scary when she takes on this expression with her question because you know Linguini won't be able to answer it properly.
Cera in The Land Before Time gives a pretty big slasher smile when she decides upon seeing what is apparently Sharptooth's corpse to use it as ramming practice. However, a few rams in, she soon discovers that Sharptooth was not quite as dead as she originally thought, and just barely managed to survive to tell the tale.
Ed the hyena (and to a much lesser extent, Shenzi, Banzai, and all of the other hyenas) actually gains this type of smile when the hyenas all kill Scar at the end of The Lion King.
Scar gives one himself to Zazu when he points out how unhappy Mufasa will be that he didn't show up for Simba's birth ceremony. After he tells him this (as well as forcing Scar to let a mouse, his lunch, escape), Scar sarcastically states "ooh, I quiver with FEAR!", flashing this smile when he says the last word, and then tries to EAT Zazu! Good thing Mufasa showed up right at that moment.
In The Lorax, at the end of the Villain Song, "How Bad Can I Be", the Once-ler has one after shouting the last lyrics, "HOW BAD CAN THIS POSSIBLY BE?!"
Atlantis: The Lost Empire: When Rourke has a pretty awesome and crazy slasher smile when he tries to kill Milo with a fire axe. You can clearly tell the guy has gone batshit insane.
In All Dogs Go to Heaven after Killer, currently trying to do everything he can to get Carface to spare his life, tells him he has a gun they can use to try and kill Charlie (for good) with, Carface breaks into a wide satanic version. And when I said satanic, I meant that literally—- his face (presumably, we're seeing him from Killer's POV) actually proceeds to transform into an actual devil's.
He also puts on a brief, but huge and sadistic one shortly after he sets fire to the platform Esmeralda is on when he tries to burn her at the stake.
In Frozen, Hans has a villainous smile as he raises his sword to kill Elsa.
Homura Akemi herselfvery, very briefly develops one in Puella Magi Madoka Magica The Movie: Rebellion as Madokami comes down to receive her to heaven. It serves as a short and extremely unsettling warning that something's about to go horribly wrong, confirmed about thirty seconds later when Homura proceeds to hijack Madoka's powers.
In Wreck-It Ralph, King Candy/Turbo sports a particularly notable one, in all of his forms.
The ever lovable late comedian John Candy had this expression on his face in Uncle Buck during the scene where he comes to the bedroom of Tia's "boyfriend" Bug to rescue Tia by drilling a hole through the doorknob, he's also holding a drill and smoking a cigar. Although generally throughout the movie Buck comes out as kind of kooky such as when he asks Tia "How would you like to spend the next several nights wondering if your crazy out of work bum uncle will shave your head while you sleep?" and where he's talking to Tia's boyfriend about burying the hatchet.
Bug: "Ever hear of a tuneup? Ah-hee-hee-hee-hee!"
Buck: "Ah-hee-hee-hee-hee! Ever hear of a ritual killing? Ah-hee-hee-hee-hee!"
Bug: "...I don't get it..."
Buck: "You gnaw on her face in public like that again and you'll be one. Ah-hee-hee-hee-hee!"
In the Tony Jaa movie Tom Yum Goong, or The Protector, one of the many opponents that Tony faces is a Capoeira fighter, who has just attacked a Buddhist temple full of innocent people, set the place ablaze, and then attacks Tony as soon as he arrives to help. What qualifies "Mr. Fake Eddie Gordo" for this trope is the fact that while he fights Tony, he laughs, taunts Tony, and openly toys with him using feints and false moves.
Donnie Darko, every single time he sees his giant bunny-friend Frank. It's a little creepy, to say the least. No teeth in this one, though.
In Tim Burton's Sweeney Todd just after the Pirelli sequence, Sweeney directs one at the Beadle. Scary doesn't even cut it. It's enough to make Jack the Ripper wet his pants. Although, like Donnie above he doesn't bare his teeth, so may overlap with Psychotic Smirk.
Mr. Sardonicus took liberal inspiration from the aforementioned The Man Who Laughs with the carved smile, but the character was much less of a sweet guy than Gwynplaine. It was up to the audience to decide whether he was a villain or an Anti-Villain - this being a William Castle film, they were polled, and a different ending would be screened based on whether they thought he should be treated mercifully. They killed him every time, and the mercy ending is probably lost for eternity, assuming it ever existed at all.
National Lampoon's Christmas Vacation has Clark Griswald become somewhat unhinged come the end of the movie as his idea of a "perfect Christmas" gradually disappears; his smile, however, stays.
Galaxy Quest also makes use of this trope when Sariss, disguised as Fred, arrives on the command deck to kill off the heroes. It's a very well-played Oh Crap moment.
At the end of the third segment of the 1975 made-for-TV movie Trilogy of Terror the eponymous "Amelia" crouches down low in an animalistic manner, hiding in the corner with a carving knife. She stabs at the floor with the weapon, grinning ferally and revealing the horrific teeth of the Zuni doll.
In Oldboy, our hero spends 14 years alone in a cell that features a mirror marked with the message "Smile, and the world smiles with you." He practices a smile in the mirror through the years, without any hope or contact with another person, and it becomes quite unsettling. When he's finally released on his Roaring Rampage of Revenge, he has occasions to show off his slasher smile while doing pretty horrible things.
Megan Fox displays one at various times in Jennifers Body. Most notably after she first becomes possessed and when she appears in Needy's vision sitting on top of the chair watching her and Chip have sex.
In the stinger, Thanos has a happy thought. So he smiles.
The mask of the killer Smiley sports a stitched and bloody looking one.
A velociraptor actually achieves one in Jurassic Park. As it watches two children flee from a kitchen, it bares its front teeth in such a way that it actually seems to be grinning at them.
Castor Troy from Face/Off. When Nicolas Cage becomes Sean Archer, he makes one HELL of a slasher smile after taking drugs while seeking refuge at Dietrich's apartment.
Man of Steel: Superman, of all people, in battle. So, probably for the best that he rarely smiles the entire film. He does smile normally "at ease".
Raiders of the Lost Ark. Toht, even when Dr. Jones threatens to destroy the Ark with a panzerfaust (the German army's bazooka equivalent).
In the 2013 remake of Carrie, the eponymous character sports a rather chilling one during her Roaring Rampage of Revenge. It's especially jarring when compared to the 1976 version of the same scene, in which her face remained frozen in a look of shock.
The Unknown: Alonzo's rictus grin when he finds out that Nanon and Malabar got married is something to behold.
In the second Wishmaster film especially the evil Djinn has a perpetual smile on his face to show his joy at the people he can kill and amusement at their belief they can boss him around (he's in human disguise at the time).
Both Carcer and Mr. Teatime of Terry Pratchett's Discworld books are described as smiling like this all the time. The drawing of Mr. Teatime in The Art of Discworld perfectly illustrates this. Marc Warren does a good job with this in the TV adaptation, too.
At one point in Jingo the seriously pissed off "Vimes's grin was as funny as the one that moves very fast towards drowning men. And has a fin on top."
Lijah Cuu from the Warhammer 40,000: Gaunt's Ghosts novels has one of these. In Straight Silver, it is explicitly noted that "the most evil servants of Chaos would have killed to have a smile that lethal."
In the next book, Abnett gives Magister Enok Innokenti (one of the most evil servants of Chaos ) an even better one. His smile is so hideous that it causes physical pain and nausea in humans and his daemonic bodyguard, who has murdered millions can't bear to look at it.
Professor Moriarty, Sherlock Holmes' arch-enemy from the short story "The Final Problem." Holmes describes that, though Moriarty "smiled and blinked," there was something about the Professor's sunken eyes that made Holmes, a man who was used to danger, very glad to have a revolver with him.
In Jack Vance's Dying Earth series, the character Iucounu the "Laughing Magician" perpetually supports one of these providing a clue that his sense of humor is not exactly benevolent
Perhaps inspired by the Jack Vance example, Steven Brust's novel Five Hundred Years After has the court wizard as a minor character and he is similarly described as always smiling creepily and chuckling in a questionably sane manner.
Jaime Lannister of A Song of Ice and Fire recalls in his youth facing a particularly brutal and psychotic fighter known as 'The Smiling Knight'. 3 guesses why he is named that. Luckily even a slasher smile is no match for Ser Arthur 'The Sword in the Morning' Dayne and his greatsword Dawn.
The Hellebore family from the Tad Williams book The War of the Flowers liked these. Anton Hellebore was described as having a smile like someone who'd learned it from a book, Lord Hellebore one with absolutely no good feelings in it, and the Terrible Child had one like someone pulling up the corners of a corpse's mouth.
Creepy caretaker Heimertz from the Edgar & Ellen series has a constant slasher smile. During the Tv adaptation it is shown that he has had this smile since he was a child.
Older Than Print: Skarphéđinn Njálsson has one in Brennu-Njáls Saga. "And he grinned." is a common phrase in the story that implies that something really bad is about to go down.
Randall Flagg/The Dark Man, is described as having a grin of such good cheer and jolliness which comes across however as so unsettling the human mind seems to block it out.
Also from The Stand (where King first writes about Flagg) is Harold. Most of the other survivors in Boulder just see him as a Stepford Smiler... but the slightly damaged child Leo sees things a little differently.
It's like there are worms behind his eyes, and they're eating his brain and making him smile like that.
Jame, the heroine of P.C. Hodgell's Chronicles of the Kencyrath series, smiles like this, and it is very, very bad news. It signifies the depths of her darkness, and the author said, "In a way, everything about Jame grew out of that chilling smile."
In the Kate Daniels series, Kate is trying to enlist a man's cooperation with her plan to hunt down and kill the people who have hurt her friend.
I gave him a smile. I was aiming for sweet, but he turned a shade paler and scooted a bit farther away from me. Note to self: work more on sweet and less on psycho-killer.
Rictus in Clive Barker's The Thief of Always at first seems to be a harmless goofball who's always got a big, cheesy grin on his face - until the dark side of the Holiday House (his employer) makes itself known, and his smile becomes terrifying (if Harvey Swick had read his dictionary, he'd know that a "rictus" is the grin of a skull).
In some of the X-Wing Series and any other appearances written by Aaron Allston, Wedge Antilles has often been known to smile like this - actually, while it can be assumed that he's got normal smiles, almost any time the narration says he's smiling it's this trope. Humorless, feral. He gives it to politicians when he sees through what they say to what they mean and most often to enemies he's about to shoot down.
In the same books, "Runt" Ekwesh (being non-human) has a facial structure that even a friendly smile is described as looking like a prelude to a biting attack. He's keenly aware of this and takes full advantage of it when he wants to be menacing.
Legacy of the Force has Wedge shocked and taken aback by being discharged - Wedge, who was sixty and had been in service since the age of twenty - then realizing that people are going to try to kill him. The thought is so familiar that it steadies and reassures him, and he's able to flash someone a smile "suggesting that he was a rancor and they were made of meat".
Sometimes it's a matter of perception. In Alan Dean Foster's The Damned trilogy, the first encounter between the multiracial alien alliance's and humans highlights the differences between them and us when the human, Will Dulac, first bats the gun out of the hand of the nearest alien scout out of a self-defense reflex, then offering a handshake and smiling when he realized they weren't hostile. The sudden reflexive strike nearly broke the scout's hand, and the smile confuses and alarms them as they wonder why baring one's teeth could ever be considered a friendly gesture. They also didn't get the handshake.
Similarly played in David Brin's Uplift War when an allied alien found it disturbing that humans bared their teeth and bark when amused.
Geralt of Rivia is frequently said to be "smiling nastily," usually either to intimidate or show his supreme disdain for an idea or position that he's been put in.
Gwynplaine from The Man Who Laughs, as touched upon under the examples of The Joker and Mr. Sardonicus.
The Steel Inquisitors from Mistborn are exceptionally brutal enforcers of the Empire, and the chilling grins they have when going about their work are frequently remarked on. Anti-Hero Kelsier, leader of the rebellion, also smiles a lot because it's a way of proving that he's not beaten down, but from the point of view of his enemies (to whom he has little to no mercy) it comes off like this.
Vlad Dracula in Count and Countess. Every time he's about to kill someone with his artificially sharpened teeth, he grins at them first, just to give them a preview of what's to come.
Portia Hoechst, in Charles Stross's Iron Sunrise, is described as having this by several other characters, both good and evil, in the novel.
Skeeter Traps from Chronicles Of Magic is known for sporting these, despite being a ten year-old girl. Combined with the fact that she can kill grown men three times her size, it makes her pretty scary.
Oz: Displayed among the characters like Shillinger, Adebisi, the Aryans, Timmy Kirk, Claire Howell, etc. Manipulative Bastard Chris Keller and Ryan have done this too. Even Beecher, when he was crazy in Season 2.
An episode of Xena: Warrior Princess flashes back to the point in her past where Xena went from ruthless but otherwise sane and rational warlord to utterly psychotic rampager; she has one of these grins on her face when she snaps a Roman soldier's neck, but it's her eyes that are the most disturbing.
The Gentlemen of the episode "Hush" wear these for the entirety of their appearance. And they never talk, despite gesturing at each other as if they were talking. The entire effect is ridiculously creepy.
The Gnarl, a skin-eating creature shown in "Same Time, Same Place", pulls this off chillingly. The smile is combined with a childlike personality, and it speaks in singsong, like it's telling nursery rhymes.
Der Kindestod in season 2 who eats up kids' life force by pinning them down, extending horrible little pipes from his eyes and sucking the energy out of their foreheads, while they screamed helplessly under him.
The First does this as it's impersonating Cassie.
Angelus, Spike, Warren, and Buffy herself. She flashes a pretty smile to a group of bullies. Given some think she is crazy, others remember she burnt down her previous school's gym, and is on record for being a multiple murder suspect, is enough to make them back off.
In "Mirror, Mirror" from Star Trek: The Original Series, Mirror Chekhov pulls one of these right before the commercial break when he momentarily has Kirk at his mercy:
Mirror Chekhov: "So, keptin, you die... and ve all move up in rank. No vun vill qvestion the assessination of a keptin who has disobeyed prime Starfleet orders!"
A particularly lame episode of Star Trek: The Next Generation has Data practicing his dance moves on the Holodeck while wearing an extremely disturbing, frozen rictus-like smile.
Gowron, on the other hand, mastered this trope and showed it off in almost every appearance.
In the Enzyte Commercials, Smilin' Bob has one of the most unnatural smiles ever seen in an advertisement. It's not MEANT to be a Slasher Smile, but still... BRRR!
Toby of the Doctor Who episode "The Impossible Planet" sports a nasty one while possessed by The Beast.
The Master often wears this expression. In his last story, Ainley!Master had fangs to boot. Simm!Master perfected a dishonest politician's smile in his first episodes. After that, he got even creepier.
As did Davros in his moment of triumph in the 4th series. Well, NEAR-triumph.
Also done by the ninth Doctor when he meets the "alleged" last Dalek in the universe. Thing is, it's armour is completely shut down except for its voice and eyepiece, so what does the Doctor do but give a slasher smile and attempt to "exterminate" the Dalek.
The Fourth Doctor generally sticks to the Cheshire Cat Grin, but he does this, usually when he's pretending to be evil or bluffing about how dangerous he is - like his I Am He as You Are He gambit in "Meglos". Or occasionally when he actually is being violent, like when he snaps a man's neck in "The Seeds of Doom".
Danny Elfman practically made a living doing this in the 70's and 80's. There's hardly any Oingo Boingo music video (or film, for that matter) in which he doesn't spend a few seconds scaring the living crap out of the audience. Overly obnoxious talk show hosts occasionally got the silent treatment from him, combined with a trademark psychotic grin.
And then there's... well, everyone but the band in the video for Soundgarden's "Black Hole Sun".
As for humans, Wes gives a heroic example when he blows up team Snagem's hideout in the opening.
Slightly subverted in American McGee's Alice: The Cheshire Cat had this expression (it's significantly scarier than the Cheshire Cat Grin his other incarnations wore), but he was one of the few allies the player has in the game, and he never attacks Alice. Still, when he appeared and disappeared grin-first, followed by his crazy eyes, it was prime horror. It was never quite clear whether he was as mad as a box of frogs, or frighteningly sane. Considering the game takes the idea about Wonderland as a construct of Alice's mind to it's conclusion by making Alice batshit insane herself either possibility ends in horror.
Alice herself demonstrates one near the end of the game's trailer.
The Doom guy makes this expression when he picks up a new weapon.
In the opening of Suikoden II, Luca Blight has one of the most frighteningly evil Slasher Smiles imaginable, bordering on horror (a look that he keeps consistent throughout the game) and isn't just holding an axe or a knife, he's holding a decapitated head.
Adon also has a permanent one, although he's actually a subversion because aside from the evil grin, he's not insane or Ax-Crazy.
The not so well known variant of Ken, known as Violent Ken, has one permanently plastered on his face. His altered nonchalant sounding voice and relaxed fighting stance makes him even creepier. His best attack involves screaming like a psychopath and panting heavily at the end just to seal the deal.
Magaki in The King of Fighters XI has a terrible smile frozen on his face the entire time you fight him.
Two bosses in Wario Land 4, Cractus and Spoiled Rotten, twist their faces into grotesque, rabid grins after they've been hit several times. The freakiness is magnified by the fact that their heads alone take up more of the screen than Wario does.
The Horseless Headless Horsemann from Team Fortress 2 has one of these carved into his jack o' lantern head, as well as on his huge ax.
Jackle in NiGHTS Into Dreams is constantly wearing one plastered over his otherwise invisible face. You kind of get the picture that he's absolutely insane, because just adding that evil cackle... *shudder*
Alice from the same game appears to have this as well. The way she occasionally switches from her typical smiley expressions to her evil-/scary-looking one in a single instant is so creepy it makes her bear an uncanny resemblance to a certain aforementioned mask salesman...
Barbatos Goetia displays a very unsettling one for his "No Items Ever!" mystic arte in the PS2 remake of Tales of Destiny.
The little ghosts that appear mostly in Pumpkin Hill, and dotted around other stages in Sonic Adventure 2 each have a rather creepy, fanged, smile.
Karel of Fire Emblem is an Anti-Hero with this. He's also something of an Ax-Crazy guy, considering he both constantly talks about loving to kill and he also murdered his whole family so he could get a sword. By the way, he looks like this ◊.
Paxton Fettel has one of these plastered on his face almost constantly.
The Yume Nikki fangame .flow has some of these, as shown in this walk-around video (video link) — for example, there are quite a few shark-toothed, bloody-grinning white blob things (whose faces are otherwise featureless) in the area first entered at 1:20, and the painting at 15:14 is of a surreal abstract line-art slasher smile.
There are also at least two places in .flow where the walls are made of those slasher-smiling white things, their mouths open even wider, and in one place it looks like their skins are strung up with the smiles still in the middle... even worse, the entrances to these places are the mouths of the white creatures. There's a video of these areas, too (video link) — one of the areas is entered first at 1:11, and more of it and the second area are shown starting at 7:40.
When the re-occurring character known as 'Smile' is struck with the steel pipe, he gets one of these. After the event occurs, Smile will grin every time you pull out the pipe in front of him... (for the morbidly curious, here's the recorded event: video link
Several kinds of heartless have permanent smiles plastered on their faces.
In Persona 3, the Thirteenth Shadow of the Death Arcana (Nyx Avatar) sports a mask which is nothing but a pair of hollows for eyes and an immense grinning mouth; this is in contrast to other Major Arcana Shadows, whose masks are either inhuman or emotionless. Ironically, it spends most of the fight speaking in a defeated-sounding monotone.
Issachar also suddenly sports one of these when he begins to turn into a demon.
Certain levels in WET has a random mook charging Rubi, who promptly shoots them. Blood sprays onto her face, which triggers Rage Mode and she wears a psychotically evil slasher smile throughout the level.
Another, arguably better-known example can be found in Arthas Menethil after he becomes the Lich King. In almost◊ every◊ piece◊ of official artwork where his face is clearly visible, he is generally shown wearing a grin that is in no way healthy. In fact, this seems to be his stock expression whenever he isn't wearing his helmet.
Matt Engarde shows a particularly disturbing one when you make him show his true colors in the second Ace Attorney game.
In InvestigationsShih-na gets a bit of one when unmasked as one of the villains before eventually going on to a full-blown Higurashi-style Evil Laugh.
As does Manfred von Karma, although it's only slightly creepy unless you know that he murdered Edgeworth's father. AAI doesn't specifically spell it out, most likely to avoid spoiling those who haven't played the original game, but to those in the know it's creepy.
In Dragon Age, both hurlocks and genlocks sport permanent Slasher Smiles and it's arguable that Shrieks also have one.
The fake Colonel from Metal Gear Solid 2: Sons of Liberty, during his conversation with Raiden nearing the end of the game, occasionally gives off a Glasgow-esque grin (akin to Heath Ledger's Joker character or Dissidia's redesign of Kefka Palazzo.). Justified, as during these occasions, the Colonel's face often takes a form resembling a skull.
Jetstream Sam's introduction scene in Metal Gear Rising: Revengeance comes with one of these. It just looks wrong on several levels, Uncanny Valley inclusive, but this is probably intentional to add an additional sense of unease to him.
Raiden also sports several in the same game, after reawakening his Jack the Ripper persona.
In Metal Gear Solid 3, Colonel Volgin flashes quite a lot of these, usually before cheerfully committing acts of depraved cruelty and evil. His most memorable slasher smiles occur when he nukes his own country just for the hell of it, when he sees that Snake has lost bladder control because of how intensely he's being tortured, while saying "Yes! Yes! ''That's'' what I want to see!" His other most memorable one is when he controls the Shagohod, and, while laughing maniacally, mows down his own men, again, seemingly just because he can. A lot of these traits are why Volgin is one of the few villans in the Metal Gear franchise to have next to no fans who sympathize with him, because he has no Freudian Excuse, no underlying issues, other than an extreme and insatiable sadism.
In BlazBlue, Jin gets to sport one of these whenever he's around Ragna.
In the sequel we have Hazama/Terumi who's smile is perfectly fitting for his batshit insane personality. Especially on the Japanese audio track.
Dimentio in Super Paper Mario is heavily implied to have a constant smile especially when committing very atrocious acts such as murder.
Rajan shows one in Sly 2: Band Of Thieves before the title card for "The Predator Awaits" episode, (and for the picture for the chapter) Dimitri shows one to a lesser extent at the end of his intro scene, along with crazy ass eyes.
Schwartz, the protagonist of the second generation in Agarest Senki 2 sports this when he is about to kick someone's ass all over the place.
Red Savarin of Solatorobo gets an absolutely crazy one when The Order is given. His usual upbeat, happy-yet-stubborn demeanor means it's even creepier.
Found on one of the last fictional characters you'd expect in Epic Mickey. Should you decide to take the troublemaker path with Mickey himself, he'll begin to crouch low and sport one of these grins, looking all the more like a rat than a mouse in the process.
Doctor Minoru Kamiya in Yu Yu Tokubetuhen flashes one of these when using his scalpel attack.
The dragon in Dra Koi has a slasher smile for her default smile. The protagonist kind of hates it, even in the good ending.
Kotonoha, in the one of the bad endings of School Days. The one where she kills Sekai, more specifically
Sekai also gets one in another of the bad endings when she kills Kotonoha.
Gilgamesh of Fate/stay night shows off a particularly disturbing one of these after making the Holy Grail manifest in the U.B.W. story route. For a 'yippee, destruction and fire!' variant, watch the activation of his best Noble Phantasm, or get an eyeful of this image◊.
Corpse Party has several. There's possessed Ayumi, Kizami, Sachiko, and the shadowy creature at the end of Chapter One (if it catches you)... who turns out to be Sachiko's mother.
The Jägermonsters (clawed, fanged, monstrous super soldiers) from Girl Genius have been known to do this - and most of them are on the good guys' side.
The eponymous heroine herself, though not a violent person, is also prone to sporting a scary grin when she's in the "madness place", i.e. in the throes of a bout of mad SCIENCE! And when she does, the Jägermonsters stay out of her way...
She also sports this smile fairly often when possessed by the Big Bad.
The comic's resident bloodthirsty maniac, Bangladesh DuPree, breaks out one quite often. When she does, run.
Gil, too, when he's in a really bad mood. Or when he knows something bad is going to happen... to you.
All the Sparks do it any time they go into The Madness Place. Along with the changing speech bubbles, it's the biggest visual cue.
Vriska Serket of Homestuck wears the biggest shit-eating smile possible as she waves Tavros's severed legs in front of him, just before impaling him on a lance and throwing him off a cliff.
That's at least a semi-comedic example, since both Vriska's expression and gesture are just too ludicrously twisted to be taken seriously... but if you're interested in an example played bone-chillingly straight, why not say hello to Gamzee?
Mr. Ohm has done things in high school. Whatever it was, it can't be good. Not with that sharky smile of his...
Emperor Luca deSadar from The Meek gets some wide, toothy smiles while debating an ambassador from another country about the other country's recent history of genocide and torture against his people. It doesn't help that it's been strongly hinted that Luca suffered those tortures personally, or that the author has specifically stated that big, toothy grins are not associated with good humor in his culture. See for yourself.
The twin kittens in Best Ed give these all the time, the only time they DROP their smile is at Buddy the Squirrel, who gives an Oh Crap moment whenever they do.
William Dunbar, of all people in Code Lyoko displays this while in Lyoko while possessed by XANA after the ending of the third season. This is helped by the fact that he is given a BFS to use as weapon while backed up by Monsters.
Later on in Season 2's "Lesson Zero", Twilight Sparkle's Sanity Slippage results in a rapidly-worsening succession of disturbing Unsmiles. Taken out of context, these can result in some severe horror. This is probably the most famous "smile" she gives.
Discord from Season 2 also gives a nice one when he pretty much Force Chokes the mane cast.
Then there's Princess Cadence Actually an impostor in "A Canterlot Wedding, Part 1" when she imprisons Twilight Sparkle.
Trixie gives a nice one in the beginning of "Magic Duel".
Rarity gives a pretty good one in Inspiration Manifestation when she shows off her new dress line she made while under the influence of the eponymous spell.
Kim Possible herself sported one of these at the end of her movie, right after she kicked Shego into a high-voltage electrical tower to what seems to be her death, crushed under said tower. However, she survives, frizzled and still smoking from the electrical shock, but without any major injuries. The shot showing this originally wasn't present, which made it look like Shego was killed. Test audiences were horrified, leading to the inclusion of the shot where she and Drakken are arrested and taken to jail.
She also flashes one to Drakken before flattening him (and not for the first time) as well as to Jim and Tim when she thinks of the idea of soccer being a contact sport, when she thinks of using her Super Speed in Queen Bebe, and maybe a few other instances. And she's the good guy.
Sponge Bob Square Pants wins a prize. He waits for it at the mailbox for an impossibly long time. He finally gets it, and it turns out to be a toy. Patrick, his idiot starfish friend, "breaks" it. Spongebob just has a frozen smile on his face as he looks down at it. The smile stays on the entire following conversation:
SpongeBob & Patrick: It's beautiful. (Patrick touches it and its springs pop out) Patrick: SpongeBob? SpongeBob: I waited so long... Patrick: SpongeBob? SpongeBob: And you broke it... Patrick: You okay, buddy? SpongeBob: Yes, yes I'm okay. Patrick: (sighs) For a sec, I... SpongeBob: YOU! YOU RUINED MY FREE TOY!!!
ReBoot's Hexadecimal had many masks with different emotions, with which she expressed herself, but her Slasher Smile mask is arguably the most (in)famous of all. Scarcely an episode went by without her using it at least once, and she always insisted on sticking her face right up against the camera when she used it.
In the season 2 finale Megabyte gives one to Bob before launching him into a web portal.
Near the end of an episode of Family Guy, New Brian actually does give this when he tells Stewie of him using Rupert the Teddy Bear for his pleasure, giving out the most evil slasher smile he ever gave.
Stewie gives one in "A Very Special Family Guy Freakin' Christmas" when he gets his picture taken with Santa.
Angelica of Rugrats would sometimes indulge in one of these.
Actor Jack Black can be seen with these in a wide number of photos.
The "literally smiling from ear to ear" disfigurement smile as evidenced by characters such as Kakihara in Ichi the Killer, Gwynplaine (of the aforementioned The Man Who Laughs), and The Dark Knight's Joker is commonly referred to as a "Glasgowsmile" and is not a terribly uncommon humiliation injury by gangs. The actor Tommy Flanagannote Actually from Glasgow, Scotland. sports one of these courtesy of being jumped outside a pub in his younger days.
In Japan, legends abound of the kuchisake-onna (口裂け女), a female onryou with a surgical mask to conceal it and who is hellbent on returning the favor to every male she accosts around sundown
Great White Sharks, the serial killers of the ocean. They actually stalk their prey, just like a serial killer — or like any natural predator.
Pittsburgh Steeler receiver Hines Ward is known for two things. The first is blocks so vicious and they made a new rule to try to keep him from hurting people. The second is almost always smiling. No matter how hard he gets hit, or how hard he hits someone, he gets up smiling like a lunatic.
Mug shot of the Tucson, AZ shooter, Jared Loughner◊, who killed six people and injured fourteen.
Snakes are a semi-example; they don't actually smile, but many look like they have a closed-mouthed smile. Both the green and black mamba have this face, and they are not nice snakes at all. Of course, if they open their mouth, things just get worse.
Crocodilians. Crocodiles in particular have interlocking teeth which makes it look like they are grinning.