After Hiroshi in Alive: The Final Evolution took the Heart of Akuro he became almost literally Made of Air; actually he was made-of-nothingness, his power was 'void' and that was what he was, despite wreathing smoke-stuff into an image of his old body on a regular basis. His former best friend Taisuke punched through the not-really-there body a couple time before he accepted this, and had to do some serious leveling on his heat/life/existence power in order to stop Hiroshi from destroying the world.
The Female Titan also has both; she can cover parts of her body in an extremely hard crystalline substance, hard enough that no one ever manages to break it, and she can also regenerate. However, she can't cover her entire body in crystal or else she couldn't move.
The nations in Axis Powers Hetalia can be injured, have been shown being wounded at several different times, and at least some traumatic events can leave scars on their bodies. However, it seems to take a lot more to hurt them than normal people, and they appear to heal very quickly. It seems that they cannot be killed as long as their country still exists. What happens to them when their nation is gone is unclear.
Dark Schneider of Bastard!! takes this to ludicrous levels. His primary means of defense seems to be a shield spell called "Dispel Bound", which produces a number of shields to block any attack aimed at him. Each shield can take up to the force of a nuclear blast before breaking. And they can only be targeted one at a time. And they auto-regenerate. And he can repair them manually at positively absurd speeds. And in the unlikely event that you manage to get through that, you have to deal with his durability which allows him to take attacks that can destroy galaxies. And should you somehow manage to pierce these defenses, he possesses obscenely powerful healing abilities (of the sort that makes Wolverine look like a girl scout) and finally, he still can't be killed unless you destroy his body, spirit and soul in three different dimensions at the same time. Even when he ripped out his own heart he still didnít die!
In Black Lagoon, Roberta fulfils this trope during her first appearance, when she is basically an Expy to the Terminator and the only thing that can stand up to her is Revy and Balalaika's Badass Army after running through enough obstacles to kill the rest of the cast many times over. In the Roberta's Blood Trail OVA she single-handedly tears her way through practically everything in the hunt for the American Grey Fox Unit, only to have the trope horrifically subverted. Though she kills or makes stretcher cases out of half the unit, she loses a leg, her left arm, two fingers off her right arm, and an eye in the process.
Most Shinigami are very hard to kill. Captains take this one step further, however. Their opponents have to be uniquely powerful to even harm a captain, let alone defeat them.
The evil counterparts of the captains, the Espada are this by hollow standards, especially the top four Espada who require even captain-class shinigami to group together against them or (as in the case of Ichigo versus Ulquiorra) to find a new power upgrade during the fight to win.
Both Ulquiorra and Nnoitra, though, take this up a notch. Nnoitra's Hierro, the iron skin all Arrancar sport, is specifically noted to be the toughest of all the Espada, and considering he's only ranked fifth, that's saying something. Ulquiorra, meanwhile, boasts an extremely strong regenerative ability in his Segunda Etapa form. As long as his organs and head are intact, he can regenerate from it.
The Quincies are extremely tough thanks to Blut, a technique that channels reiatsu through their veins and arteries to either boost their attack power or their defensive power. Blut can protect them from truly severe injuries.
Chiropteran Queens and their Chevaliers from Blood+ are capable of quickly healing almost any wound. This includes being impaled through the stomach with a tree trunk, stabbed with many large sharp implements and having arms cut off. If bad turns to worse and they are poisoned by Saya's blood, Chevaliers have the option to amputate themselves and obtain replacement limbs.
Lovecraft from Bungou Stray Dogs can shrug off basically anything. In an early appearance he's seen getting shot in the torso and hit by a semi (the latter visibly disfigures him, but he fixes himself rather easily. When Dazai and Chuya go up against him, it takes Chuya's full strength, a bomb that Lovecraft had unknowingly devoured prior, and an accidental reveal of his weakness by Steinbeck to finally take him down... and it still doesn't stick. Some time after the fight he gets up, completely unharmed, and goes home.
Captain Bravo from Busou Renkin via his Kakugane ability of Silver Skin that is, at least as seen in the series, completely impenetrable and even immune to the Big Bad's life drain.
Victor, Ikusabe, and Moonface all also qualify. Victor shrugs off most of what the Alchemists throw at him and regenerates any actual damage, Ikusabe has regeneration that surpasses anything else in the series, and Moonface can continuously duplicate himself as long as one body remains intact.
A Certain Magical Index has more than a few examples of people with powers that let them fall into this trope. Of course, since The Hero has an Anti-Magic right hand, they're far from invulnerable to him. At least one, Hyouka, would probably die at mere contact.
Touma himself possesses an odd form of invulnerability: Extreme luck, or lack thereof. He's so unlucky that the world won't let him die.
Accelerator has the power to change the vectors or force or energy of anything he comes in contact to in any direction he pleases, resulting in a perfect Attack Reflector. It's been noted that a nuke might be able to kill him. The explosion and radiation wouldn't do squat; he'd be in danger from suffocating due to lack of oxygen.
Hyouka is the other prime example. She's actually very easy to damage... it's just pointless to do so. She isn't human and only has the outer appearance of one, so if you explode half of her she'll just reform. If you explode all of her, she'll still reform because she's basically a solid projection. It apparently still hurts though.
The Windowless Building in Academy City. It is completely sealed to the outside: no entrances, no windows, recycles its own atmosphere, not even radiation or heat can get in or out. The only way in is through teleportation (and everyone suspects it has countermeasures against that too if necessary). It is famously said to be able to take a nuke without being damaged in the slightest. At one point Accelerator throws a skyscraper at it with the force enough to shatter the planet several times over. It's completely unharmed afterward.
There are so many characters with this trope that counting them all here would take all day. Letís just say that some characters in this series are so ridiculously overpowered to the point that only a few people can even as much as see them and survive. note To elaborate, a character that can erase your sin of hurting others, completely nullifying your ability to hurt other people, is one of the lesser invulnerable characters.
The demons in Chrono Crusade are the Regeneration type, at least the high-power ones. Their ability to heal themselves is so strong that one demon manages to quickly regenerate (with some help from a magical jewel) after being so severely wounded his stomach was sliced open and his intestines were spilling out. They do have some weaknesses (including holy water, grave head injuries, and having their heart removed from their body), but it takes quite a bit to truly kill them.
Claymore manages to mix Made of Diamond with Made of Plasticine. Awakened Beings can ignore attacks from people who are capable of slicing solid stone pillars in half, but anything they can't outright ignore goes straight through them.
Offensive styles can pull themselves back together, while Defensive styles are supposedly able to regenerate limbs. The characters themselves also seem to be undaunted except when the story says they should be.
Priscilla's true strength instead is her extraordinary regeneration, so powerful that it is said to be closer to "creation" rather than normal Claymore regeneration. She has survived tremendous attacks, her head being cut in several parts (in a setting where cutting the head is usually the only way to guarantee that something will stay dead) and even her entire body being shattered into pieces!
C.C. from Code Geass. She has survived burnings, tortures, bombings, bullets to the head, not to mention drowning at the bottom of the ocean and being crushed by the massive pressure. The only way to kill her is to take her Code, a mark of immortality, and the only ones who can do that are those who have awakened Geass in both of their eyes.
Also, V.V., and later, Charles vi Britania by taking V.V.'s. However, Lelouch proves that the above spoiler isn't the only way to kill an immortal: he "convinces" God/Collective Unconscious/Source of Geass to kill Charles.
In a way not connected to the above two, Marianne vi Britannia can use her geass to live forever, via 'Grand Theft Me', stealing a new body whenever she pleases. In the end, as above, Lelouch "convinces" God to kill her.
Many of the villains could regenerate. The Namekians' had this ability although it's fairly constrained compared to the following two, as they could only regenerate if their brain was still intact. Cell however, due to his unique genetic make-up, can literally rebuild himself From a Single Cell after blowing himself up. Buu (who is also a Blob Monster) is even more extreme. He was blown into a million pieces, and then had each piece vaporized; he regenerated from the vapor. He also came back from a planetary destruction (that he caused). Frieza could survive with most of his body destroyed, although his lack of a regeneration ability meant that he had to make do with cybernetic implants, falling under External Repair. On a side note, pretty much every major fighter was also Made Of Diamond, mostly because they could use their gigantic powers to shrug off damage. By the time of Z, the heroes are so strong that it's easier to kill them by blowing up the planet they're on than by overpowering them.
Goku's near indestructibility is often Played for Laughs, especially in the original Dragon Ball, like him being shot, run over, falling out of the sky, hit with blunt objects, crush, eating, set on fire, and receiving little to no damage. He is so indestructible that Goku often let his opponents wail on him just to see how powerful they are. This is Down Played more in Z, but still shows up from time to time. Like being the only fighter not to be destroyed by Buu, being able to take a full beating from Frieza and still able to fight and go Super Saiyan, and able to hold Raditz while all his ribs are broken.
This trope can be Subverted without a power difference. It's been stated several times throughout the series that no matter how tough someone is, if they lower they guard they can be hurt or killed. More often Played for Laughs with Master Roshi getting a blade stuck to his head and Goku being hurt by a rock as a Super Saiyan. It is Played for Drama when Vegeta knocks out Goku for several hours because he relaxed his guard and Sorbet piercing Goku's heart in Resurrection 'F. As Whis puts it, the body is incredibly fragile when emptied of ki.
This trope is relative in the series. A fully defensive Super Saiyan, even the weakest ones in the series, could take forces far exceeding the entire nuclear arsenal of our world without a scratch on them, but because of the ever escalating nature of threats, what was once nigh invincible (and still is in comparison with many other series) can be taken out with one shot by the new bad guy.
In "Super", the reigning king of this trope is Zen'O, the Top God of the multiverse. The Supreme Kai outright says that nothing can kill him, no matter how strong. This isn't just because Zen'O is The Omnipotent: Future Zen'O unleashes a multiverse buster to kill Merged Zamasu, who'd merged with the multiverse and become an reality encompassing Eldritch Abomination. Merged Zamasu was immortal and still destroyed by it, but despite being at ground zero of the blast, Zen-O is completely untouched.
Shizuo Heiwajima from Durarara!! is a minor case of the Made of Diamond variety from high-school onward. Shinra hates the prospect of operating on him because he's more likely to break the scalpels than actually cut him open.
Zeref. He's a 400 years old mage that carries a curse that makes him pretty much immortal. But, this curse also carries a caveat: if Zeref values life around him, all life in the radius of some miles around him will die. The only way for him to not insta-kill everything around him is for him to not value life, but...at that point he will probably kill people anyway, this time with his own will and his own insane magical powers. He said that this curse can be broken and he can be killed, but there is no proof whether this is not just him trying to convince himself that he can die, since he wants to die.
The Dragons themselves were all but invulnerable to anything aside from natural physical damage and their own kind's Dragon Magic (and even then both had to be some really high-level, as in the kind only another dragon could usually dish out). Anything else would at best just get them to flinch a bit. The Black Dragon Acnologia is only vulnerable to the former, thanks to the fact he's unaffected by and even eats Magic itself, including Dragon Slayer Magic.
Agni, the main character in Fire Punch, is basically immortal. He was born with super regenerative abilities, meaning even if a limb gets cut off, it will regrow eventually. Then he gets set on fire by magical flames that burn the target until they are dead/incinerated. Thus, he is always on fire, but even that cannot stop him. Even decapitation won't keep him down forever.
However, he still feels pain. After being set on fire, he spends 8 years simply starting to cope with the agony of eternally being on fire. However after that, he is able to shrug off pretty much anything pain wise.
For that matter, Al falls under "external repair." He's a soul bound to a suit of armor by an alchemical rune painted on the inside of his neck. Although he's hampered as you'd expect by damage to other body parts, as long as the rune's undamaged, he's still alive, and with a bit of work, can be repaired through alchemy — although care must be taken not to damage the rune in the process of making the repairs.
All Homunculis can regenerate from ridiculous injuries; however, certain homunculi have other defenses in addition to this. Greed's Ultimate Shield was Made of Indestructium by using the carbon in his body to cover himself with a layer of material as hard as, and tougher than, diamond. (Ed cleverly got around this by transmuting the carbon into a softer form.) This also contributes to Father's defeat by making the Father's body Made of Plasticine.King Bradley's Ultimate Eye lets him see the outcome of any given situation before it happens, so he is very good at dodging just about anything. This is especially helpful in the manga, where he is the only homunculus who doesn't have regenerative powers.
Out of all of the Homunculi, the very toughest and hardest to kill is probably Sloth. They only manage to temporarily stop him by dousing him in tank fuel and exposing him to sub-zero weather, causing him to freeze solid.
Van Hohenheim, like the homunculi, has the ability to regenerate any damage, since he is a living Philosopher's Stone.
The Big Badhas the same regenerative ability as Hohenheim, has blob-type invulnerability in his One-Winged Angel form, and can use alchemy without moving to block just about everything coming at him. They only manage to take him down by triggering a Superpower Meltdown.
The spare parts thing is a standard ability for cyborgs from Gunnm/Battle Angel Alita. If the heart/lung systems are still connected to the brain and neither are too banged up they can survive almost anything and wait indefinitely for repairs (the lead spending literally centuries in a scrapheap after a fall from orbit).
If a cyborg has a brainchip, ALL bets are off! Such as Alita herself in Last Order.
In Guyver, the main character, with the aid of his suit, has been shown to survive having a chunk of his brain blown off, to completely obliterated save a few traces of brain matter on his suit's control medal.
The tribe of Heroes in Heroic Age fall under the Made of Diamond category of this trope.
Up to Eleven. These are creatures that have no problems surviving blows powerful enough to shatter moons.
Alucard from Hellsing has extraordinary regenerative powers, being able to build himself back up from a pool of blood.
Alucard's invulnerability is directly tied to his familiars (undead creatures created from the life stolen from the people whose blood he has drank). He stores them within his coffin, and there are millions of them (due to his advanced age and particular bloodlust); while his familiars are contained within himself he possesses their collective life, making him very difficult to permanently injure. When he summons his familiars, he personally becomes more vulnerable, although he can recover from injury by deferring damage to the familiars, at the cost of gradually destroying them.
At the end, he gains Schrodinger as a familiar and gets rid of all of the others. This gives him the ability to exist so long as he is aware of himself (It wasn't easy. It took him 30 years to find a way around the Critical Existence Paradox associated with absorbing an entity that was both everywhere and nowhere). This moves the already pretty invulnerable Alucard somewhere closer into god territory as the only thing that seems likely to be able to kill Alucard is himself committing suicide. That or maybe an actual god.
In Hell Teacher Nube, Nube, Tamamo, and the schoolgirl Ayumi can all project their astral bodies at will, as well as shape it as they see fit. Nube and Tamamo often use it to pose as elementary schoolkids, while Ayumi simply does it to attend school with her friends... as well as to role-play as a Magical Girl. Since these are purely spiritual projections, they can be twisted, smashed, blown to bits, sliced to ribbons, crushed, and incinerated (They often are, but always for comedic effect.) They just pop right back, no worse for wear.
An even more extreme case is with a Buddhist nun who wants revenge upon the mermaid, Hayame. Since she atemermaid flesh, she is invulnerable to nearly all damage, including blowing half her own head off with grenades, getting burned to a crisp, or getting her torso crushed into a bloody mess. The amount of punishment she goes through (all of which is her own damn fault, since her psychotic methods tend to backfire) would be terrifying and gruesome if it weren't absurd to the point of hilarity.
Youkai in InuYasha are apparently made of invulnerable. Ignoring those who can project forcefields and those who design their own bodies and throw away weak parts, they just don't seem to die from normal causes. Inuyasha, a halfbreed, can completely heal from wounds that should be mortal in less than a day, and there are examples of them living for days without their heads. It seems to take either holy energy, destroying their heart (which they might be storing outside of their body), or a more-powerful youkai effect to directly destroy the source of their life force to do it. The chief villain Naraku spends much of the storyline building up better and better layers of invulnerability in an arms race with the heroes' evolving abilities and weapons.
This trope is rampant in JoJo's Bizarre Adventure, mostly in the form of regeneration. Dio Brando, his vampire servants, and the Pillar Men who spawned them can regenerate from any amount of damage, and can really only defeated by the sun's power.
At the end of Part Two, Karsovercomes even that weakness, becoming completely invincible. He was able to survive even being at the center of a volcanic eruption, and was only defeated by blasting his still-living body into space.
Part 3 also has Rubber Soul's stand, Yellow Temperance, a flesh-eating blob monster that's impervious to damage. In the end, it's beaten by Jotaro ignoring it and just attacking Rubber Soul directly.
Part 3 also has Justice, a stand that's made of fog, and thus can't even be touched. It's eventually beaten by getting inhaled by Star Platinum, exploiting the Synchronization inherent in stand abilities by causing its user to suffocate.
Part 4 has Sheer Heart Attack, an automatic stand in the form of a tiny tank, that tracks down the warmest object in the vicinity and then explodes. Contrary to user's belief, it has some weaknesses, though it's still absurdly sturdy. Star Platinum, whose punches can crush things more durable than diamonds, continuously punched it with all his power for several seconds, hitting it so hard, that he actually damaged his fists in the process, and that still wasn't enough to stop it.
Superfly from part 4 also qualifies - it bound to a steel telephone tower and can restore any damage, that has been done to it by repelling it back - meaning, that attacking it is not only pointless, but also dangerous, since all atacks will be reflected back to you.
Part 5 also brings us a notable example in the form of the stand Notorious B.I.G., which was actually activated by the user's death, and as such could not be killed. It was brainless, but relentless and unstoppable, absorbing any blows and regenerating from any damage. It simply attacked whatever was moving fastest around it, and was never truly defeated. All they could do was ditch it into the middle of the ocean, where it continued attacking whatever was moving fastest around it, perpetually chasing waves. According to the narrator, occasionally ships go missing in that area of the ocean, and it's why.
Then there is Giorno Giovanna and his ultimate stand, Gold Experience Requiem. Giorno becomes so broken it could even handwave Gurren Lagann's attempts on it. "No matter what ability, it will not happen". It can revert anything, icluding enemy attacks and abilities to zero, meaning that whatever you trying to do to him simply won't work, regardless of what that is. This thing has no weakness and you'd soon want to commit sepukku than let it kill you, because it's also erases your death, forcing you to die over and over again, forever. Truly a terrifying power if it was only given laser beams.
Part 6 has Yo-Yo Ma, atomatic stand with acid saliva, who simply refuses to die, regardless of what has been done to him. He was shot in the face several times, punched through the head, had his skull cracked open and sliced open (both times with large portions of the brain being destroyed) - and all of that been regenerated in seconds, barely slowing him down. He disappeared only after his user was killed.
Eclair of Kiddy Grade combines two different tiers of indestructability. Firstly, once her powers are fully realized, she can project extremely powerful forcefields, up to and including clawing her way out of a black hole. Secondly, as an ES Member with the support of Chief Eclipse, she can be resurrected whenever she winds up dead anyway - the exact details aren't made clear, but it's got something to do with reading and storing quantum patterns to be reimprinted later. In all appearance, nothing short of being completely broken down to her component particles can permanently stop her. And if her eternal partner, Lumiere, is present, even that won't work, due to Lumiere's ability to control any particle, which somehow allows her to reconstitute both herself and Eclair after they've been completely reduced to subatomic particles.
Akuma Shogun of Kinnikuman uses everything but extreme luck in a single fight. His armor is made from combining the bodies of the Six Devil Knights, and if injured he simply ejects and re-absorbs them to Regenerate. He can change his "Choujin Hardness" to make his body harder or softer as needed. The result is that if caught in a hold, he can become Made of Rubber/The Blob to squirm out of it, or to power up can become literally Hard as Diamond to strengthen himself. It's shown that within his armor is nothing, meaning his body is actually Made of Air so most techniques can't even harm him because there's no body to harm. To top it all off, he's also a god. His ultimate weakness is his head, which controls all of the above. But even then, getting in a blow strong enough to significantly damage it is no small feat.
The Gauna in Knights of Sidonia consist of two parts, the Placenta and the True Body. The Placenta is a Kaiju-sized mass that can transform into pretty much any kind of matter and regenerates rapidly, only stopping when the area is depleted of Heigus Particles or when the True Body is destroyed. In the former case, the Gauna is merely disabled for a time, not killed. The True Body is a human-sized object that is completely invulnerable to any damage not caused by Kabi; even blowing up a gas giant around it won't scratch it.
Keitaro in Love Hina is a humorous example, as he's effectively invincible despite suffering constant attacks from all the girls, plus Amusing Injuries such as getting punched off of a third floor balcony or getting hit by a car. It's lampshaded on several occasions when other characters encourage him to jump from a car onto a plane about to take off, telling him not to worry because he's invincible. On another occasion, he jumps off of a cliff to save Naru, and tells her afterward that he would probably survive, but she wouldn't have. The one time when this fails him is when the top of one of the buildings at Tokyo U falls off and lands on him, breaking one of his legs and putting him on crutches for a while.
Reinforce herself as the humanoid avatar of the Book shrugged off seemingly everything thrown at her (they didn't bust out the Arc-en-Ciel then) and was ultimately defeated not by brute force but by Hayate taking her body back.
Vivio's Sankt Kaiser form took the Made of Diamond route with her Saint's Armor. With it, she can shrug off Nanoha's attacks like they were nothing, despite Nanoha using Blaster Mode. It took five Starlight Breakers fired at the same time, each amped up to even more ridiculous levels by a maxed Blaster Mode, to penetrate her Saint's Armor and destroy the Relic inside her. And she was still conscious afterwards.
Hardgore Alice can regenerate any damage done to her. Blow a hole in her stomach, decapitate her, burn her to ashes, nothing will kill her unless every molecule of her is destroyed. She's killed when she's attacked in her powerless human form.
Swim Swim transforms her body into a liquid form, meaning all physical attacks such as fists, swords, and bullets simply phase through her. Light and sound can still injure her however, and she's killed when a flash grenade renders her unconscious, knocking her out of her Magical Girl form.
Yumenoshima Genopsycho possesses an invincible suit. When her visor is down, absolutely nothing can damage her, not even being soaked in lava or being hit by a disintegration beam. Her suit is invincible, but she is not. She's killed when an enemy is able to hit her body directly, ignoring her suit.
Sonia Bean can disintegrate anything she touches on a molecular level. This includes a ship dropped on her, fire, and poisonous gas. Nothing can touch her. Despite all their powers, Magical Girls still have to breathe. She's killed when she's trapped in a bubble which has its oxygen ignited, ruining her concentration and causing her to be burnt to a crisp.
Tepsekemei assimilates with the wind, so all physical attacks will go right through her, similar to Swim Swim. Despite the presence of Sonia Bean and an anti-magic barrier, she actually survives her ordeal unlike most other near invincible Magical Girls.
Grim Heat's ability is to ignore rudeness. More specifically, nothing is allowed to touch her unless she gives permission. Physical attacks such as halberds and explosions completely fail when used against her, mental attacks are unable to affect her, and if she's somehow brought to another world where a particular Magical Girl is a Physical God, her powers still take priority. She's arrested by the Land of Magic, and her transport explodes, supposedly killing her. Her body isn't found, so many doubt she was actually killed.
Colonel Sanders made himself invulnerable by using an illusion during the tournament. In other words, Made Of Air. Though Kaede mentions that she knows a few things that could dispell the illusion, though. She just didn't use them because she had no proof that Sanders was a bad guy (for the record, he wasn't).
Evangeline is also pretty much invincible due to the fact that her vampire powers allow her to regenerate any damage. On at least one occasion, she's been impaled by a chunk of rock about an inch narrower than her torso, and she was more mildly annoyed than anything else. Healing does take some effort, though, so it is presumably limited.
The Humongous MechaMazinkaiser is literally indestructible - it withstands several fights, falling into a volcano and atmospheric reentry (including a crash landing) without a single scratch, at the very least. Eventually the enemy catches on, and devotes their efforts to trying to kill Kouji when he's outside of his machine.
Its predecessors -Mazinger Z and Great Mazinger- and Grendizer were also nigh indestructible, but not to the levels of Mazinkaiser. Still, Mazinger-Z whitstood a nuclear blast at point-blank range, and Great Mazinger was even sturdier. However, they ultimately subverted the trope Dr. Hell crafted increasingly more powerful Mechanical Beasts were capable to seriously harm Mazinger. And the Mykene War Beasts ultimately destroyed Mazinger-Z, and they often damaged Great Mazinger severely.
Medaka Box's Kumagawa, who's Minus "All Fiction" makes the laws of causality his bitch. Anything that could potentially hurt him has no lasting effect, including death itself. It doesn't matter if you dropped a building on him, he'd just walk it off. Even after trading away "All Fiction" for "Book Maker", he still managed to survive being stabbed, shot in the head with an antimateriel rifle, tazed, doused in sulfuric acid, and cut up with rusty gardening tools. And that didn't even keep him down for a day.Turns out it's partly because he still has a remnant of "All Fiction" that lets him cheat death.
Immortals and Lost Souls from Mermaid Saga fit the Regeneration/Resurrection variety, with the only things able to kill them being decapitation or complete destruction of the brain. They also are capable of limb reattachment, which the series often uses for disturbing results (all together now, guys: face replacement!)
Rin Asougi from Mnemosyne takes the cake with this, as its literally impossible to kill her permanently, not even by pushing her through a JET TURBINE, unless she is devoured by a very specific type of creature, which she has been shown able to handle on her own.
Well the angels are one thing, but then we have the guy who kills immortals and angels by removing their Time Spores.
That character is revealed to be both an angel (aways male) and an immortal (always female) due to be being a hemaphrodite so it was easy to do.
Played for laughs in Mobile Suit Gundam 00, with Patrick Colasour. He's a barely competent pilot who often goes up against the main characters, who are slaughtering enemy combatants left and right. Patrick, however, always survives getting shot down, usually without a scratch on his body, attributed to Extreme Luck. In the second season he's even mockingly nicknamed "The Indestructible" because of the sheer number of battles he's survived despite losing.
This is a fairly common trend in Naruto for villains.
Gaara is a strange mix of Made of Air, Made of Diamond, The Proxy, Fighting A Shadow, and Divine Protection. His Tailed Beast, Shukaku, was initially believed to be protecting Gaara by using sand contained inside the gourd on Gaara's, but this protection is so strong Gaara is incapable of physically harming himself. Later on, this turns out to be his mother's will that was protecting him all along.
Made of Diamond: Kimimaro had a bloodline that made his bones harder than steel and was able to use them as armor anywhere on, or in, his body. The most damage he suffered from attacks (including his own) was the loss of some skin, which he also seems able to heal rapidly. The Third Raikage is also this, as his skin itself seems to be so hard that he can withstand Wave Motion Guns. The Susano'o of Mangekyo Sharingan users and the chakra cloak of jinchuuriki are also this.
Made of Air: If he can react in time, Tobi can allow solid attacks to phase through his body for up to five minutes in a row. However, he's vulnerable when attacking because he can't have different parts of his body be tangible and intangible at the same time. Also applies to Konan, who is made of papers.
Regrowth/Regeneration: Orochimaru could simply 'shed' his damaged body like a snake, forming a new, intact body. Even if a body is suffering permanent damage he can just get a new one. Combat medics like Tsunade and Kabuto have techniques that can instantly repair all of their wounds in the middle of battle. Kakuzu is also this, as he can continue to regenerate himself so long as his heart(s) are still intact.
External Repair: If Kisame is injured, Samehada can fuse with his body and use the chakra it has eaten to heal him, even from injuries as severe as having his chest blown open.
Multiple Bodies: Pain has six bodies; unless all six are dead at once, he can just find new ones to replace the ones that die and come back at full strength later, and one of the bodies can restore the others instantly. In fact, even that isn't enough, because the six bodies are actually being remotely controlled by a real seventh who doesn't go anywhere near the combat (thus really being a case of "by proxy").
Body Surf: Sasori, who had made himself into a puppet, uses backup bodies. So long as his core isn't destroyed, said core will continue to use spare puppets as new bodies.
Divine Protection: Kakuzu's partner, Hidan, was genuinely immortal, and simply needed severed appendages sewn back on. Word of God though is that malnutrition will eventually kill him.
Resurrection: Izanagi grants the power to temporarilywarp reality to render any and all injuries (up to and including death) during the duration of Izanagi into illusions. The user's body will fade into nothingness, ad they reappear again somewhere around.
Virtually all of the Angels in Neon Genesis Evangelion are Nigh Invulnerable in some way. Most are simply Made Of Diamond, but there are variations, such as Made Of Air (Leliel), Hive Mind (Iruel), Regeneration (Sachiel) etc.
More specifically, the AT Fields generated by both the Angels and the Evas are more or less invincible, and can only be breached by mind-boggling amounts of power (or another AT Field). But without that protection, both Angels and Evas can (and do) get badly hurt quickly. However, Zeruel was Made of Diamond even underneath its AT Field, if taking the equivalent of a tactical nuke at point blank range unharmed is any indication.
Finally, the Evas themselves are tough as nails to fight, and have a whole underground secret base dedicated to their external regeneration should they take too much of a beating. Unit 00, for example, takes that same nuke at the same range, and only loses its arms- though it is unable to act, the fact that it is still standing says a lot about the Evas' toughness. No matter how much damage they take, it seems that they can be brought back to full working order, given time.
Made of Diamond: The Whitebeard pirates third division commander "Diamond" Jozu is literally Made of Diamond. Kaido is also so indestructible they had to let him go after trying to execute him dozens of times, and has taken up suicide attempts as a hobby, including 10000-meter jump to the ground. He just left a Kaido-shaped crater.
Made of Rubber: Luffy himself is literally a Rubber Man.
Regeneration/Regrowth: The Whitebeard pirates first division commander Marco "The Phoenix" can regenerate with his blue phoenix flame, due to his ultra rare Mythical Zoan power.
Saitama from One-Punch Man is Nigh-Invulnerable. Every attack against him (that are usually done by giant monsters) doesn't even phase him. If he isn't even bothering to tank it he'll just bounce around like a destructive rubber ball without even taking a scratch, and if he does bother he's basically unmovable. He's been punched to the Moon, and just jumped back to Earth, not even winded. When the psychic alien Geryuganshoop used his telekinetic gravitation wave on him, which was said to be as powerful as a black hole, not only was Saitama not even phased by it he was actually disappointed.
The parasites in, well, Parasyte can harden, heal or move very quickly the part of the body they have infected (generally the head), which means that the only way to kill them is to attack a part they haven't infected (by stabing them in the heart, for example). But then is introduced Gotoh, a being made of several parasites covering the entire body, meaning that in addition to faster-than-the-eye-can-see-Shapeshifter Weapons, he can either block, dodge or take anything you throw at him, including high-powered shotgun ammunition, assault rifles bullets, grenades, a car and having his head cut off. Doesn't save him from a nasty fall into toxic waste though.
Word of God says that anytime the body of Kyubei dies; it can easily regenerate another one instantly from surrounding mana.
Walpurgis Night also counts. Homura hammers it with a ridiculous amount of firepower using conventional weapons, but no visible damage is shown.
Ryōga Hibiki, especially after his Bakusai Tenketsu training. Since he's thrown himself into boulders hundreds of times and gotten hit by subsequent shrapnel just as often, his body is hardened such that most common attacks are utterly useless.
The warrior Lime, retainer to the Musk Dynasty's prince, is even sturdier.
The Phoenix King Saffron can regenerate instantly from any injury via his own flame. He has only one weakness: being frozen solid. And even then, that merely stops him, but it won't destroy him: after being frozen and shattered into a million pieces, he regenerated as an egg and hatched immediately afterwards, albeit as a toddler.
In the Read or Die series, every single character with the powers of paper is essentially impossible to kill as long as a sliver-sized piece of paper is in their possession. They can make paper that can stop bullets dead, cut steel, completely block any blow, and make clothes out of it which basically means that their clothing is also impossible to penetrate. Bombs and fire also don't do anything, and several different characters can create flying machines (such as a giant paper airplane) to allow for safe travel downwards to the ground from impossible heights.. The only weakness? Water, but even then all it takes is one piece of dry paper or a dry edge and they're fine for the time being.
R.O.D the TV gives Paper Masters a secondary weakness when the Paper Sisters go up against a villain who can utilize sound waves, including one particular wavelength that disrupts their powers (though it doesn't save him from getting knocked out by an ordinary, unpowered hardcover book.) The British Library eventually uses this against them as well.
Sanosuke Sagara of Rurouni Kenshin. The trademark of his fighting style is to absorb damage from his opponents. He has taken a ball and chain to the face, and was once thrown through both of the dojo's walls, only to remark that the technique used on him was a rubbish technique. He also took a palm slap that embedded the user's hand into solid stone without even flinching.
Phoenix Ikki from Saint Seiya apparently has regenerative AND resurrective powers. Oh, and he apparenlty gets a levelup every time he comes back to boot.
3◊3 Eyes: The near-extinct three-eyed mystical creatures known as Sanjiyan Unkara have the ability to bind the souls of mortals to their own, leaving said mortal with the character "Wu" mystically emprinted on his or her forehead and the ability to regenerate quite literally any degree of damage so long as their master lives. Sadly, this results in a serious case of Immortality Hurts.
Sabrac, from the second season of Shakugan no Shana, appears to possess incredible regeneration skills, as he takes blow after blow from Wilhelmina (including being crushed by two apartment buildings before being nuked), yet regenerates each time he hits the ground. Actually, it's more of a case of multiple bodies: Sabrac's real body is hidden beneath the ground, and can recreate the body above ground each time its destroyed.
Hao Asakura of Shaman King is of the resurrection type. By the time the story rolls around, he's already been killed twice. Trouble is, he's an immensely powerful shaman who retains memories and powers gained in his previous lives and, in fact, dying actually amplifies his power further. The entire second half the series is spent trying to find a way around this. In the end, the heroes convince him to abandon his plans to kill all humans, instead of outright killing him again.
One of the Seven Stars in Corpse Princess is made of gas, meaning he can't be hurt by swords or bullets. He can also change what gas he's made of, so he can be sedative or explosive if he likes.
Zelgadis of The Slayers is a Made of Diamond version, in the context of his universe. Merged with a demon and a stone golem, his entire body is made from living rock. This makes him superstrong and a lot heavier than he looks, but also extremely difficult to hurt due to the fact that all of his "squishy bits", external and internal, are made from organic granite. It takes incredible concussive force to cause anything resembling internal injuries, and bladed weapons are useless (for obvious reasons). In the third season of the anime, he takes a cannonball to the face at point-blank range and is merely knocked out for a few seconds. Even magic isn't that useful against him- at one point, he claims that only something as powerful as the Sword of Light can hurt him, and that turns out to be a Demon Lord from another universe. The only creatures in the series that have been able to truly hurt him are the native Demon Lords and creatures of their power level.
Gourry also seems to display this trait in a fashion similar to The Tick. He gets blasted a lot by Lina Inverse (usually for saying or doing something stupid) with spells that are normally fatal and often finds himself on the receiving end of a lot of punishment, and comes out with little more than some soot on the face. Of course, in this case it's Played for Laughs.
Free of Soul Eater is the regenerative type. He's been stabbed, shot, and encased himself in ice (accidentally), and cut in two And he's still around. Oh, and Great Old Ones, such as Lord Death and Asura, also counts, due to being Physical God.
A villainess in Speed Grapher is literally made of diamond, a power apparently supported by her frequently eating diamonds (in one case, by biting off some unfortunate girl's ring finger.) In addition to the damage resistance this implies, it's difficult to focus a camera on her (the protagonist's main way of killing things.) A can of spray-paint gives him something to focus on, leaving her barely alive. Her boss subsequently determines that she's not so good against The Power of Blood.)
The Tekkamen, including the titular hero, of Tekkaman Blade all qualify for this, as part of the transformation renders them Made of Indestructium. Blade takes a military-grade nuclear warhead to the face, and isn't so much as scratched.
Viral of Tengen Toppa Gurren Lagann became Nigh Invulnerable after Lord Genome gave him immortality complete with a Healing Factor, although it only sees use once. The Anti-Spiral leader is a Made Of Air Energy Being variant, but that doesn't stop him being killed by a giant hole drilled through his chest.
Being a series about immortals, UQ Holder! has several examples, but the biggest one would probably be Karin. It is literally impossible to injure her as all damage is instantly Retconed away. This doesn't stop her from feeling pain though.
Yu-Gi-Oh! 5D's pulls out the Earthbound Immortals, dark forms based off of the Nazca lines. All seven of them (Aslla piscu, Chacu Challhua, Ccarayhua, Ccapac Apu, Cusillu, Uru, and Wiraqocha Rasca) have a special effect that renders them immune to attacks, Spells, and Trap Cards, and they can attack the opponent directly. The only way to reliably get rid of one is to destroy the Field Spell Card present on the field. Each one also has a fun special effect, ranging from controlling opposing monsters to nuking the field to cutting the opponent to one Life Point. These were not actually tuned down for the real card game, and they are bastards to try and deal with.
YuYu Hakusho: Both of the Toguro Brothers are this taken to pretty crazy extremes. Younger Toguro is of the Made of Diamond variety, as even when Yusuke finally gains equal power to him, nothing short of a full power Spirit Gun was able to damage him, and he only died from the strain put on his body. Elder Toguro is of the regeneration variety, being able to instantly repair almost any wound to his body, shift his body's physical form to dodge attacks, and shift his organs throughout his body. Even Younger Toguro reducing him to half of a head doesn't kill him, as he is able to slowly regenerate from even that. Younger Toguro also has a bit of the regeneration schtick, as his transformations allow him to regenerate large wounds in his body, as shown against Genkai.
Virtually all S-class beings in the later parts of the manga are this. Considering you have to be a Physical God to qualify as a S-class, this isn't exactly surprising.