The Death Note from, well, Death Note has as one of its lesser-known rules that it cannot kill anyone less than 780 days old, or about two years and change. Two other rules exempt people over 124 years of age, and people destined to die within 12 minutes.
Also, the Death Note cannot be directly handed to a human under 6 years of age.
Babies don't show up in Dragon Ball and its sequels all that often, but the Cell saga featured Bulma and Vegeta's infant son, Trunks, alongside his Future Badass self that came back to Set Right What Once Went Wrong. The one time baby Trunks is in mortal danger, Future Trunks jumps in to save him and his mom. On the other hand, Dende, who is roughly the Namek equivalent of a five-year-old at the time, is brutally murdered because Frieza doesn't want him using his Healing Hands to help the heroes—and this is after Frieza jumped the Moral Event Horizon by murdering Dende's entire village, including his brother. Later on, seven-year-old Goten and eight-year-old Trunks are killed when Majin Buu blows up the Earth and three-year-old Marron is turned into chocolate and eaten along with her parents and the other side characters. (This is the poster series for Death Is Cheap...)
There is a filler scene in the original Dragon Ball where Snow, the girl from Jingle Village, grabs a rifle from a fallen King Castle soldier and takes aim at Piccolo Daimao as his back is turned, but gives up. Piccolo then turns right around and fires eye-lasers in her direction. When the smoke clears, we're relieved to see that he wasn't aiming for Snow at all, but another soldier directly behind her. This scene sort of doubles as an example of Men Are the Expendable Gender.
Why? I could see if she was a grown woman, but the person killed in place of her was not just an adult, but a soldier, too. It's not like a bunch of boys from her village were being killed, too.
It is however, averted when Vegeta and Nappa first arrive on Earth. Nappa's first action is to blow up the entire city they've landed in—- which does include some children seen in the background. And the kicker? Unlike most ordinary civilian casualties, in the series they don't get brought back by the titular MacGuffin... Except in the dubbed version where they write the whole thing off as Conveniently Empty Buildings.
Daimos: Daimos averts the trope as soon as the SECOND episode. A kid spends a short while egging Kazuya and Erika on to kiss. Later, when the enemy attacks, an explosion destroys the greenhouse had gone into. Kazuya and Erika bolt to the place and find him lying between the rubble. The kid opens his eyes and asks Kazuya if he "got lucky" before dying as Kazuya is holding him in arms.
Zambot3: This series is notorious -among other reasons- because it averted the trope. Anyone Can Die. It does not matter if you are a kid; it does not matter if you are a kid and a secondary character; it does not matter if you are a kid and a MAIN character. Given this is a show produced by Yoshiyuki Tomino (as well known as Kill 'em All), it should not be shocking.
Gun Smith Cats 1-ups Mad Max in one particularly memorable chase scene. A girl runs out into the middle of the road, Bean Bandit (who has a soft-spot for kids) and Rally Vincent (hotshot bounty hunter pursuing him) avoid hitting the girl by running their cars into each other and driving simultaneously on two wheels, forming a triangle over her.
We know from when it's first found that the abandoned baby in Tokyo Godfathers will survive anything.
It's implied in the movie that the baby is getting protected by God Himself, with a nice analogy to the infant Jesus. This is probably most apparent during the climax, when the baby and Hanna fall off of a building and are saved by a huge gust of wind.
One would think that this would be horribly averted in Code Geass, but it's actually played straight for the most part if the viewer has a sharp eye. Even through throngs of crying babies that are the children of the Elevens/Japanese, all of them seem to live. In the R1 episode "Bloodstained Euphie", Euphemiaguns down a large throng of Japanese. Among the survivors are some elderly folks and thank goodness, a baby.
In One Piece, a young boy finds out that the King of Alabasta attacking Nanohana is actually an impostor, and then gets caught by Mr. 1 and Miss Doublefinger. While in most cases, it would seal his fate, they injure him and leave him for dead, enabling him to expose the truth after Crocodile's defeat.
Averted with Sabo's death. The fact that we never saw his body led some to believe that he was still alive, but Word of God confirms that he's dead.
Averted in the case that was orchestrated by the World Government where they ordered that every infant including ones not yet born that could be related to Roger to be killed on sight - including the mother and anyone related to her.
Another bloody aversion ordered by the World Government was the extermination of the city of Flavence. Only a then-10-year-old Law survived. Everyone else, including a nun who was supporting Law, the kids she was taking care of, and Law's parents and younger sister, were all wiped out by the World Government. Needless to say, this fucked Law up pretty badly.
Averted to some degree in Karakuri Circus. Children (particularly Masaru) are shown to be terribly injured on occasion...and then the French village gets attacked by the evil circus.
Averted in Reiko The Zombie Shop by child murdering psychopath Saki Yurikawa. Introduced in the first volume, Saki's a teenage serial killer who has murdered over twenty little girls. She initially takes an interest in them being her "little sister", and when they refuse she snaps and utterly butchers them. Even after her death and zombification by titular heroine Reiko children still die in this series.
Subverted in YuYu Hakusho. Hiei, minutes after birth was thrown off a floating island, into a demon infested forest. Luckily, he survived. And what's worse, it was all because he was a male.
The Ice Maidens are some kinda cold blooded to have zero pity for an infant, indeed.
The backstory arc in When They Cry has a reporter with a pregnant wife, who he left behind to cover Himezawa. He's told that by doing so, he'll come to regret it. His wife dies while he's away. In the Time Skip, we learn that they saved the baby.
Both invoked and averted in Science Ninja Team Gatchaman. A child or children directly involved with the main cast in some way will survive. The nameless, faceless children either unseen or briefly seen on the streets when a mecha comes stomping through are screwed.
Both played straight and subverted in Black Lagoon. Played straight with Garcia and Fabiola.. for now; subverted with Hansel and Gretel, and the orphans they used as decoys.
In Gaiking, the trope is zigzagged. The Tagalong Kid of the crew is put in serious danger several times and yet he lives through, and the little brother of a crewmember ( Peter's brother Tom) is taken hostage and also survives... but the younger brother of another Space Dragon crew-member ( Fan Lee) dies in the arms of his sibling after being shot In the Back, and in one of the earliest episodes a little girl named Lisa is shot to death because her father didn't want to join the Big Bad's forces.
Violence Jack averts this to harsh effects. No one is safe from being graphically killed.
Battle Angel Alita: In addition to the Crapsack World of The Scrapyard where villains have no qualms about killing children, there's also the infant-meat-fancying Venusians and the "Methuzalized" space colonists who regard "the next generation as a threat, not a promise" and regularly send death squads after children. There's also the Child Soldiers of Jeru/Ketheres, who Alita and her new friends from Mars try to save a day too late, and the orphans on the Space Karate guy's planet.
Kentaro Miura shows repeatedly in the Berserk manga that children do not get special immunity from the horrors of the story's universe.
The dead body of a little boy can be seen among the victims of the bandit leader from the first major story arc.
Later in the second arc Guts is given a ride by a kind priest and a young girl who he takes care of. The three are attacked by demonically possessed skeletons and the young girl Collette is brutally killed. She then returns possessed and kills the priest before going after Guts along with the rest of the undead. Guts then has to kill her again, along with the rest of the skeletons.
After becoming separated from the rest of the Hawks during an earlier battle, Casca reveals to Guts that long before he joined them a young boy who acted as a page to the mercenary band was killed in battle. She says it is the first time that she truly saw Griffith be disturbed and depressed by something and later is shown to have deeply affected Griffith mentally.
During the Band of the Hawks arc, Guts carries out an assassination order by Griffith on the King's brother and then is forced to kill the brother's young son because the boy saw too much, an act that shakes him up terribly — not the very least because the boy reminded Guts of...well, himself when he was the kid's age.
Judeau later points out that the son was being groomed to marry the Princess who Griffith also wished to marry (as it was the most direct path to become king). By having the boy killed, Griffith has a much easier shot at marrying the Princess and as such gaining his dream, so it is likely he planned for the boy to be there and Guts having to kill him. This turns out to be one of the factors which eventually led to Guts leaving the Hawks.
After rescuing Griffith after a year of torture the Band of the Hawk gets aid from a young family which includes several children who long supported the group. Shortly afterward, the Black Dog Knights, a group of soldiers composed of the worst rapists, murderers and criminals that Midland has to offer appear, having been sent by the King to kill Griffith. The group, led by Wyald, a truly nasty piece of work of an Apostle, question the mother before she and her family including the young children are raped and killed. And if that wasn't bad enough, they then proceed to dismember their bodies (yes, including the kids) and carry them naked on poles into battle with the Hawks, who are all disgusted at the sight.
That said, Rickert, the youngest of the Band of the Hawk, is the only other survivor of the Eclipse besides Guts and Casca, and that was only because he was separated from the main body of the Hawks before Griffith's Behelit activated, otherwise he would have been branded and eaten along with the rest. He did almost die when the below-mentioned Rosine and the Count from the third manga story massacred the men with him, but he was rescued by the Skull Knight.
The Misty Valley arc main villain Rosine started out as a cute, smart tomboy with a horrible home life who loved a certain fairy tale. She later sacrifices her parents to the Godhand and becomes a elf/fairy creature similar to that found in her favorite fairy tale and begins to attack the nearby village killing people and animals and kidnapping children to turn into twisted little elf/fairy creatures that play kickball with eyeballs, play war to the death, and rape each other for fun (remember they are still technically children and are acting in a twisted way like the kids they are.) By the time Guts reaches her, she is insane, and has to be killed in order to prevent her from hurting any more people (and given that Guts is still in hardcore post-Eclipse vengeance mode at this point, all he really cares about is killing another Apostle). During the arc you see that she Used to Be a Sweet Kid who only wanted to have some happiness that she never got at home turning into a case of Alas, Poor Villain especially considering that once she dies, she, like anyone who makes a sacrifice to the Godhand and becomes a demon, is sent straight to hell.
Also, those eyeball kick balling, to-the-death war playing elf/fairy creatures that Rosine made from kidnapped children? When they are killed they turn back into kids, leading to Guts being seen as a child killer.
Guts himself did also indulge in a bit of child-mass-slaughter. Sure, they were forcibly polymorphed by Rosine and reverted to human form upon death, but he KNEW that, and he was still grinning maniacally while he crushed them.
And also, there's Rosine's Morality Pet Jill, a somewhat younger girl that calls her "older sister Rosine" ("Rosine-neechan" in the original Japanese). She survives the arc, though not before being in lethal danger at least twice.
In the Millennium Falcon arc, women and children in a village are constantly kidnapped by trolls. The woman are raped till they become pregnant with more trolls, but the rotting bodies of children skewered on poles are seen in the den.
As the trolls are being subdued by Guts, those captured escape with the rest of his party and many children are seen with them, acting as a slight subversion.
And collectively, the most disturbing case in the series so far is what happened to Guts and Casca's own child. When Guts returned to the Hawks and before the crew set out to rescue Griffith, he and Casca had an emotional reunion that ended up with them making love, with said union resulting in Guts impregnating Casca. Though pregnancy was unknown to them at the time, it's assumed that the baby was developing normally in the womb... until the Eclipse happened. When it goes down, everythinggoes down, with Griffith, now the demon lord Femto, raping the pregnant Casca in front of Guts, tainting her womb with his demonic seed and thus poisoning her unborn child. After the Eclipse, the now traumatized and insane Casca undergoes a miscarriage from the event, resulting in a misshapen fetus being born that has been corrupted by evil. Guts, seeing the child as nothing more than a byproduct of an event he failed to prevent, tries to kill it immediately, but because of Casca's intervention, the child disappears at daybreak.
In Bleach, there's this whole deal with a little boy having his soul separated from his body and placed in a parakeet's body by a Hollow...
We see ghosts of children several times, their deaths are not shown on screen though.
Blue Gender. Things don't go well for poor Yung, and during the massacre of Yung's group by the Blue, we see one of the Big Creepy-Crawlies slash at a mother holding an infant (Mom dies; kid goes flying). Needless to say, if the blow didn't kill the baby, hitting the ground will.
In Code Geass, (albeit, off-screen) as Britannian soldiers are gunning down Japanese, the viewer hears a crying infant, followed shortly by a hail of gunfire.
Also, there's several instances in the general massacres scenes where you can see smaller bodies, clearly of children and teenagers, albeit undetailed and from a distance.
The raid on the Order of Geass.
The EarlofMillennium doesn't care how old you are; as long as you lost someone close to you, he will be there to turn you into an Akuma.
Detective Conan occasionally touches on the deaths of children, though always in the backstory providing a motive for the current killer. The closest it has come to killing a child on-screen was the start of the sixth Non-Serial MoviePhantom of Baker Street, which starts with a ten-year old Child Prodigy jumping of a skyscraper.
Horrendously averted in Devilman: Two of the worst deaths are destined for Sachiko, Akira's little neighbor, and Miki's younger brother. In fact, in regards to Devilman and Devilman Lady, Go Nagai has absolutely NO compunction about killing children and babies in the most horrific way possible and showing it very clearly, preferably in front of their parents.
The Grendizer manga (also a Go Nagai production) has a villain who averts this twice- in a flashback he kidnaps all the kids from planet Fleed and says he'll give them back in exchange for the planet's weapons. When they give up the weapons, he gives back the kids- by dropping them from 30,000 feet in the air. And in the present, he steals Great Mazinger and ties up a bunch of kids as well as people Duke cares about all over the robot so Grendizer can't fight back.
There's also an episode of Mazinger Z where Shirou's crush, Lorelei, was a Robot Girl with the body of a 10-year-old cutie... and in control of a huge mecha beast. She doesn't make it. In another, Sayaka's cousin Yuri (who is actually crippled) is kidnapped and placed inside a capsule in a mecha beast's head; she's luckier than the others, though, and survives.
Also averted in Violence Jack. The first arc alone is filled with graphic deaths of young kids.
Lucy from Elfen Lied has no problem killing children in the most horrible ways, including the male protagonist's little sister Kanae. Also young Diclonius children get killed off regularly, often in gruesome experiments (leading to a notably heartbreaking scene in the anime).
Averted in Ergo Proxy, when viewers are treated to a baby carriage falling down a flight of stairs in slow motion during the mall chase early on in the series; very much a shout-out to Eisenstein's Bronenosets Potemkin 'Odessa stairs' scene. Later, the carriage is shown lying on its side in a puddle of (presumably the baby's) blood. However, that is certainly not the only baby to die in Ergo Proxy. (Not a spoiler. Really.)
Then there the shot of a mother actually smothering her crying infant just before some Corals find them and kill them both. Once again that was a Gory Discretion Shot. Plus the scene when Dominic tries to go looking for a replacement for Anemone.
Several children die in the manga, but are spared in the TV series (notably Bat's younger brother Taki, who is murdered by one of Jackal's men; and Ryo, the kid at Shuu's hideout who died eating bread that Souther and his men poisoned). Strangely, the TV series "made up" for it by having several adult characters who survived the manga die instead (like both Harn Brothers instead of just Haz). In the first Raoh Den movie, the child-poisoning scene is restored.
In contrast to the TV series, the original 1986 movie shows a group of nomads being massacred by camouflaged thugs while wandering the desert. The casualties include a young mother and her infant child.
Yet for some reason Pride, a hundreds-of-years-old monster wearing the skin of a child, is the only surviving homunculus at the end of the series.
In a strange ironic Hilarious in Hindsight way the same character, Selim, died at the end of the 2003 anime version. Also, though a bit older than usual, Edward dies in the 2003 anime (twice) only to be brought back (well..not the "Real world" Edward though).
Averting this is Genocyber's claim to fame, to the point that the most brutal and obvious example has ended up on at least one shock site.
Rin's first appearance has her being brutally and graphically slaughtered by Kouga's wolves. Thankfully, she gets better.
Oh, and much later on? She gets dragged into Hell. Again, she gets better.
Kohaku. Not only was he brainwashed into killing his dad and fellow Demon Slayers as well as injuring his older sister, but then he takes a fatal attack for her and dies. Then he's revived. But is Brainwashed and Crazy. And it takes him a LOT to get better.
Averted in the seventeenth volume of The Kindaichi Case Files, "The Undying Butterflies" in which a twelve-year-old girl is the first victim of the story's murders.
In Mobile Suit Gundam The 08th MS Team, Shiro and his team are completely sickened when they see Zeon soldiers gun down a mother and her child for leaving their house at night.
Zeta Gundam specifically showed an infant body in the gassed colony 30 Bunch, and a mother and infant child are briefly shown dying when the Titans use the Colony Laser to destroy several colonies as a "demonstration".
Mobile Suit Gundam SEED doesn't shy itself from averting the trope either both with the girl that gave the origami flower to Kira being killed in the explosion that Yzak caused when he shot the refugee shuttle in which she was. There's also the shot of a dead mother and her child in the ruins of Junius 7, which either shocked or caused a complete breakdown to the characters who entered the room where these bodies were.
This idea is destroyed in Neon Genesis Evangelion. By the end of the series EVERYONE is dead (sorta). some 14 year olds have suffered multiple, rather hideous deaths (impaled, eaten alive, impaled some more, then killed).
Averted offscreen in Noir, in the Intoccabile episodes, when a Mafia traitor gets questioned by the titular Intoccabile, with his wife and child in the next room to ensure his cooperation... and both get shot due to his hesitation. Also, Mirielle's older brother died when he was a young child in the assassination that killed her parents.
In the Space Runaway Ideon movie, even the kids perish. Special mention goes to the scene when a little girl is beheaded by a gunshot onscreen. Poor, poor Ashura.
In Venus Versus Virus in one arc one of a set of twins gets turned into a Virus. She asks Lucia to kill her so she doesn't harm her brother.
In Mai-Otome, Mimi, a young girl who is part of the refugees of Windbloom, dies from her wounds after being attacked by a desert monster.
Muhyo And Roji's ghosts are often children, who die of causes such as falling onto a subway train tracks, fires, car accident, or even suicide, or parents who lost their children. The moment of their deaths is often shown in flashbacks.
In Mirai Nikki, Anyone Can Die, even children. The 4 year old Reisuke is killed by Yuno, and later on Yukki's 14 year old friends are all gunned down as well.
Although a lot of their ages are ambiguous, and many are too old to count, The 8th's orphanage is slaughtered.
The Tsukihime manga featured a chapter when one of the antagonists invades a hotel, using his powers to kill anybody. He passes by a pair of children and it looks like he'll let them live...till his monsters chomp on them too.
Hunter × Hunter: This is how the Chimera arc starts, with a pair of sibling coming across the queen who eats both of them.
Averted seven ways to Sunday in Franken Fran, where kids die in nasty ways : a little girl gets her head bitten off, a boy from the same chapter is mutated into a monster by a virus and killed by the remaining survivors, another girl from a later chapter is stabbed in the head... Some chapters play it straight, though.
Amanuma from YuYu Hakusho thought his ability just made games realistic, but Sensui didn't tell him everything that happened in the game would actually happen. He died when Kurama defeated him, since that is what happens to the boss in the game they were playing.
Horrifically averted in Blood+ by Saya, who impales a baby within the first minute of the series.
The fourteen year old protagonist of Deadman Wonderland is constantly in danger but never really gets hurt. His classmates on the other hand are all brutally murdered within the first ten pages of the series. Hibana Daida, a seven year old, once tortured and killed a boy in kindergarten because he flipped her skirt. Hibana herself is killed by Toto.
Toboe was actually the first of the Wolf's Rain wolves to die. He's the youngest, being roughly thirteen to fourteen in human form.
Averted in Kill la Kill, where Ragyo Kiryuuin is shown conducting horrible experiments on her newborn daughter, and then, when the experiment fails and she dies, drops her down a trash chute in the laboratory without even giving her a name. But it's then subverted when it's revealed that the newborn daughter was actually Ryuko, the protagonist!
JoJo's Bizarre Adventure both plays it straight and subverts it in the first part. On the straight-up scale, this is how Jonathan and, later, Lisa Lisa live to maturity. On the subversion scale, Dio is confronted with a mother that begs him to kill her and spare her baby. He takes her up on it. Unfortunately for the kid, the now-vampirized mother is both ravenous and lacking in maternal feelings... Thank the gods the scene cuts away at that point.
Later, an old woman with the power to control the dead and wounded uses corpses as weapons, needing to only wound someone once to win a fight. The corpse that deals a wound? It's a baby. Using its tongue. As a knife.
Surprisingly enough, Attack on Titan plays this trope straight almost across the board. Children are implied to die on a regular basis, but so far there's only been one on-panel portrayal of a child being killed. More accurately, a youth approximately 10 - 12 years old being bitten in half by a Titan with blood splattering everywhere and his legs kicking as he's Eaten Alive.