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.
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.
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.
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.
All of the homunculi in Fullmetal Alchemist can regenerate; 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. The 2003 anime's Sloth can change herself into liquid, and is an example of intangible. In the end she is paralyzed by her mortal remains and Ed transmutes her body into Ethanol that evaporates away into the atmosphere.
Van Hohenheim, like the homunculi, has the ability to regenerate any damage, since he is a living Philosopher's Stone.
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.
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.
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.
Many of the villains in Dragon Ball 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 recovered from having his entire upper body destroyed, and later literally rebuilty himself From a Single Cell after blowing himself up. Buu (who was 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 mid-series, the heroes are so strong that it's easier to kill them by blowing up the planet they're on than by overpowering them.
This is a fairly common trend in Naruto for villains.
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 the only attack capable of penetrating it is his own.
Divine Protection: Kakazu'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.
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").
Regrowth/Regeneration: Former member 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. Naruto can also regenerate from wounds that would kill most people, though unlike the medics, he can't heal other people.
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 with her paper jutsu and Suigetsu with his water jutsu.
Izanagi grants the power to temporarilywarp reality and, as used by Danzo, basically renders any and all attacks that connect useless, because they fade into nothingness soon after.
The Proxy: Sasori, who had made himself into a puppet, combined Spare Body Parts with a backup body. Naruto, too, has a habit of doing this with his Shadow Clones.
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.
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: Susano'o when used by Sasuke, Madara, and Itachi. The V2 Chakra Cloak when used by the Jinchuriki. Naruto's Nine-Tailed Chakra Mode cloak and Biju Mode Cloak.
Most True Ancestors can locally reverse time to regenerate their bodies, even if they're completely blown apart. Arcueid was even able to revive after being killed Deader than Dead by Shiki at the beginning of the story, albeit by rebuilding her body from scratch at the cost of most of her available power.
Ciel is unkillable for the duration of Tsukihime. As explained, because Ciel is the previous host of Roa, and Roa is still alive (knowing Reincarnation and all), the world itself will not let her die to prevent a paradox from occuring. Ciel herself possesses extreme regeneration abilities.
One of the antagonists, Nero, has a body composed of pure "chaos", and contained within are 666 beasts. If they are killed outside of his body, the chaos will return to his body and regenerate; he only dies when all 666 lives inside are destroyed at once, making him practically indestructible. Even if you hit him with a force that can destroy continents, he'll still probably have 100 lives or so left.
In the sister universe Kara no Kyoukai, Aozaki Toko has a replacement body, which is completely identical to her original in every way. It's even flesh and blood, apparently, and only activates when the original body is killed. Don't bother trying to figure out which is the real one. It's a bit confusing.
Even the Mystic Eyes ofDeath Perception wielded by Tohno Shiki has limitations. ORT, which is already canonically the single strongest being in the Nasuverse, cannot be affected by it due to it having a completely different 'concept' of death than humans and Gaia. (Theoretically Shiki could eventually figure out the concept of a Mercurian death, but it's far more likely that his brain would be reduced to mush first.) Arcueid herself has no lines or points of death under a full moon, and in her Archetype Earth form, even Ryougi Shiki, whose own M Eo DP are even more horribly broken than Tohno Shiki's, cannot find any lines or points.
While all the Servants of Fate/stay night can probably fall under this category to some degree, special mention must be made for Berserker, aka Hercules who, thanks to his Noble Phantasm, God Hand, not only can't be affected by any non-fatal attack (an attack of at least A-rank, in terms of power, if memory serves), but regenerates until you kill him 12 times. Yes, you read that correctly, he has to be killed 12 times in order for him to truly "die" as a Servant.
And it makes him resistant to any attack that manages to kill him, so he has to be killed in twelve different ways in order to finish him off, although some really powerful attacks can take multiple 'lives' at once.
One of Saber's Noble Phantasms is Avalon which grants her passive regeneration and prevents aging, and when activated it shifts her into another plane of existence, making her completely immune to all forms of attack. Unfortunately, it was stolen from her while she was alive, so she doesn't get to use it. It eventually ended up implanted inside Shirou, which is the reason why he survives all the crazy shit he puts himself through.
It is extremely unclear whether or not Ultimate Ones can truly be destroyed. It is said that some of them (like the aforementioned ORT) are so alien that death is simply something that does not happen to them (as it's arguable as to whether they are "alive" in the first place), and the few who have been "killed" have continued to exist in some form or another.
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.
Alucard from Hellsing has extraordinary regenerative powers, being able to build himself back up from a pool of blood.
Alucard's rival/opposite number Father Anderson is only marginally less resilient, having readily shrugged off large-calibur bullets into the brain.
Alucard's invulnerability is directly tied to his familiars (undead creatures created from the life stolen from the people whose blood he has drank) of which there are thousands (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 ExistenceParadox 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.
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.
The spare parts thing is a standard ability for cyborgs from Gunnm/Battle Angel. 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.
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.
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.
C.C. from Code Geass, being immortal, literally cannot die. 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 that requires such specific guidelines that it's practically impossible to do unless she wants to die.
Which she does.
Also, V.V. and Charles di Britannia. The latter of whom proves that the above spoilers are not entirely true, by killing the former and becoming immortal. And then finds out that the above spoilers are not true again, and his son, Lelouch, "convinces" God/Collective Humanty/The 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.
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.
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.
And then being killed by a giant hole drilled through his chest.
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!)
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.
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.
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.
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, Carsovercomes 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 Five 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". This thing has no weakness and you'd soon want to commit sepukku than let it kill you. Truly a terrifying power if it was only given laser beams.
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.
One of the Seven Stars in Shikabane Hime 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.
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.
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.
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.
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 and none have so far been killed.
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.
The Quincies are also extremely tough to injure as they possess the ability to push reiatsu through their veins and arteries to either boost their attack power or their defensive power. Their defensive power can protect them from truly insane injuries.
Aizen fused with the Hogyoku which ensured he could keep regenerating even wounds that should have killed him. Later, it's confirmed even Ichigo's Story Breaker Power can't kill him. As long as the Hougyoku is fused to him, he's officially regarded as immortal.
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.
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!
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 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.
The title Claymores are given a kind of mixed-bag.
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.
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.
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.
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.
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.
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 at several times the speed of sound. It's completely unharmed afterward. Aleister Crowley uses it as his personal fortress.
Fraulein Kreutune survived over a hundred trials by ordeal, and is relevant to the plot because she is completely indestructible.
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.
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.
Yu-Gi-Oh! 5Ds 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.
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.
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. Fire also shows itself to be essentially useless, as it will chip away at the paper (which is more to be said than anything else in the series), but the paper is basically flame-resistant while being used by a Paper Master. 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. The characters themselves however when unarmed are typically well trained in some form of martial arts or acrobatics training (especially Anita King from R.O.D. The TV who can backflip, somersault, and single jump to the top of large bookcases around a library like she's been doing it all her life dodging bullets), making them still deadly even when unarmed. The only time the characters are shown as easy human people are during the comedic episodes, any other time they are protrayed as unstoppable single person armies unable to truly be stopped even when in a bad position and often times can beat down an entire building's worth of opponents equipped with everything from guns to lasers without breaking much of a sweat.
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.
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.
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.
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.
Captain Bravo from Busou Renkin via his Kagugane 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.
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.)
And then there's Hades, who makes Gajeel look wimpy in comparison.
Zeref demonstrates this once he stops giving a damn about human life, thus regaining full control over his powers. When Natsu swung his new magical sword at Zeref's head, the sword's blade snapped off while Zeref wasn't even scratched. He's also a centuries oldimmortal.
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.
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.
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.
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.
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.
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.
The Female Titan 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.