"It'll take more than being tied to a lit keg of explosives and tossed into a pit of acid filled with mutant, acid-resistant flying piranhas equipped with flamethrowers and battle axes while venomous, mechanical, missile-launching Morris dancers armed with liquid hydrogen harpoon guns are overhead; riding giant rabid killer bees with side-mounted death rays to kill Othar Tryggvassen!"
Simply put, damage is frequently done to characters that really, really should hurt or incapacitate them, but is easily shaken off. Nobody ever breaks a rib or other bones unless that specific broken bone becomes important later on.
Note, this isn't Super Toughness or Nigh Invulnerability, where the character actually is supernaturally protected from harm. This is the ability to shrug off blows that would disintegrate a human body when you technically shouldn't be able to. So Robots, Mutants, Mages, Ki using Martial Artists, etc. do not count. Having a story-enabled reason for not being a bloody smear immediately takes one out of the running for this trope.
It can also be argued that certain Required Secondary Powers may also induce this. It is particularly true for Super Hero characters to have "increased strength and endurance" in their portfolio, even if never outright explained or stated. How else can someone whose sole power is throwing flame take being thrown off a multi-story building as no big deal? The line really gets fuzzy between Badass Normal and Charles Atlas Superpower where somehow a "normal" person has become invulnerable to the effects of Real Life by apparently just willing themselves uninjured. Modern special effects are somewhat to blame for this, as they frequently up the forces involved to look more dramatic. This sometimes approaches cartoon-esque extremes, such as a person getting smashed through concrete or brick walls and being able to get right back up again with only negligible injury.
By extension, blunt damage, concussions, and other side effects of "non-lethal" fights or a Tap on the Head never have unintended fatal consequences — death can only happen with intentionally-lethal weapons, like swords or guns. And even with normally-lethal weapons, the hero may intentionally inflict flesh wounds instead of shooting to kill.
This trope also allows our hero to take a bullet in some critical area (chest, shoulder, etc) and continue to fight as though nothing had happened, even if they should be Overdrawn at the Blood Bank.
It also makes you wonder why, for all the supposed beatings they have received themselves over the course of a show, the hero/heroine never suffers any long-term scarring or lasting physical injury. One especially tenacious example is the lack of punch drunkenness, with Nancy Drew and Jimmy Olsen getting knocked out several times in each of any of hundreds of adventures with no long-term brain damage to show for it. Indeed, unrealistic lack of damage from head injuries leads to the widely prevalent subtrope: Hard Head.
Punch-drunk boxers are the classic real-life example of what happens to someone who takes repeated pummeling damage in many fights year after year. However, the American National Football League presents a better sampling. To survive more than a couple of seasons in the league is a guarantee of a lifetime of painful, lingering damage to battered joints, bones, and connective tissues. That life is also going to be about ten years shorter than that of the average adult American. The heart and body organs build up scar tissue likely to fail when the athlete is in his fifties and sixties. A condition known as Dented Iron.
Between them, Made of Iron and Hollywood Healing cover the two main varieties of action hero — the Terminator-type that can walk unscathed through a bomb-blast, and the hero who does get hurt badly but somehow always manages to come back and triumph in the end.
The polar opposite of this is Made of Plasticine. When the character doesn't just shrug off extreme damage but doesn't sustain any damage at all is Made of Diamond, a subset of Nigh Invulnerability. Characters who are Made of Iron, if they die at all, often die Rasputinian Deaths. If two Made of Iron characters go up against each other, it often leads to How Much More Can He Take fights. Not to be confused with Maid of Iron.
A character who is Made of Iron isn't necessarily literally made of iron.
If a person has this kind of durability as a superpower, it's Super Toughness. When the character does sustain grisly, incapacitating injuries but somehow manages to keep going anyway, it's Normally, I Would Be Dead Now.
In the Jackie Chan Adventures fic Queen Of All Oni by the same author, this version of Jade has increased strength, a Healing Factor, and increased durability after her transformation, and has been thrown through walls and down hills and gotten right back up afterwards (she claims she DOES bruise, but it can't be seen against her skin).
Clash Of The Elements: Alex Whiter has a ridiculous record of getting hit with attacks that would kill any normal human, which is a bit crazy considering that in spite of his flight he only has an above-average level of strength. Of course, when one takes into considering his Determinator status...
Gru from Despicable Me. He was able to survive the rockets and missiles from Vector's base, with the exception that he's completly covers with ash.
Nigel from Rio. Although he survived the turbines of the smuggler's plane, he lost most of his feathers and was made fun by the marmosets.
Kent Mansley of The Iron Giant is always getting bashed into things but manages to pop back up again. Maybe he's just that serious about stopping the robot.
Jack Skellington of The Nightmare Before Christmas manages to get shot down by anti-aircraft flak guns without being blown to pieces. This could be justified, however, by the coffin sleigh taking most of the blow. However, this does not explain how at least a mile-high fall onto a stone angel didn't break any of his bones (the impact from the fall did seem to be strong enough to knock off his jawbone, however). This all still could be justified by the fact that Jack's undead, so he would not feel pain, if it weren't for an earlier scene where Sally accidentally pokes Jack's finger with a needle, and he yelps in pain. It's a little confusing.
Because he personifies most bruiser tropes, it's no surprise that Popeye was Made of Iron back when he got his start on Thimble Theatre. In his first few story arcs, Popeye takes some brutal beatings and manages to come out on top. When in one fight he takes several handgun rounds in the gut, he manages to still win the fight before passing out. In the hospital, in addition to the bullets that put him there, knife blades, tips of pool cues and many, many other indications that you should see the other guy.
Professional Wrestling can wander into this when things go wrong and sometimes even when they go right, generally missed completely by the tendency for people to think "knowing how to fall" equates to "falls don't hurt." See Hell in the Cell, where Mick Foley suffered a concussion, broken ribs, and a dislocated shoulder after falling from a twenty-foot height twice, and still finished the match.
Another great example is Kurt Angle. For the uninitiated, he was in the summer Olympics with a broken neck. No, he didn't get it during the wrestling tournament, he had it before the tryouts. Not only did he convince them to let him compete, he won the gold medal. While he's at times injury prone, his neck at least is made of titanium. This is an understandably large point of pride both for his character and in real life.
"I won an Olympic Gold Medal with a broken freakin' neck."
Japanese female wrestlers can take piledrivers, powerbombs, and DDT's from the top rope onto steel chairs and tables, several times in the same match.
The Undertaker. At Elimination Chamber 2010, Taker was making his way to the ring in his usual grand fashion (Smoke, fireballs, really slow walk, etc.). Undertaker did his usual pause at the top of the ramp, and was engulfed in flames by an errant fireball. Playing it off as being fired up, he ran to the ring, and proceeded to wrestle an entire Elimination Chamber match. He then lost his World Heavyweight Championship to Chris Jericho, but nobody's perfect.
Wouldn't you believe it but Zack Ryder has become one. In the month of January 2012, he's been assaulted by Kane in ways that other wrestlers his size would be dead by now. He's been dropped from ten feet in the air, had three powerbombs on his cracked ribs, got chokeslammed through the stage before finally having to be put away with a Tombstone Piledriver by Kane at the Royal Rumble before he has to be put out for a while.
Chris Jericho has only suffered two serious injuries to his body in his entire life. One was a broken arm caused by his own stupidity (practicing dives without a mat). The second was a herniated disk, which he suffered training during Dancing With The Stars. Keep in mind he's been in more Elimination Chambers than anyone else, been in more than a few brutal TLC matches, worked for several promotions that specialized in Garbage Wrestling, and works a hard-hitting, high-risk style in which several peers have destroyed their own bodies.
Olympic skier Hermann Maier's spectacular crash at the 1998 Winter Olympics in Nagano, Japan. High winds caused an unintentional ski jump. He flew through the air, hit the ground headfirst at 70 miles per hour, bounced, tumbled, and smashed through two wire-and-slat fences before coming to a stop. And then he picked himself up and walked back up the hill, rubbing his shoulder (he also had a minor leg injury). A few days later, he won gold medals in two events. A news article about the event began with the words, "The Tough Man contest is over. Forever. The winner is Hermann Maier." And he almost lost his leg after a traffic accident but continues to win — his nickname "Herminator" is well deserved.
Hockey player Gordie Howe was said to get a goal, an assist, and a fight in every game. He continued playing in the NHL into his fifties, even through its notoriously violent era, long enough to play with his grown sons. After his retirement, he even suited up for a charity game in the minors, whereupon a local radio DJ offered a large cash prize to any player on the opposing team who fought Howe, by then in his seventies. No-one was stupid enough to take up the offer.
In a similar vein, Toronto Maple Leaf Bobby Baun scored the game winning goal of game six of the 1963-1964 Stanley Cup finals after sustaining a broken ankle earlier in the game.
Jake Brown, 2007 X Games skateboard contender, lost control of his board and fell 45 feet to the deck below (clip is here). After a dazed few minutes, he got up and was able to walk out under his own power.
George Chuvalo, a former heavyweight boxer, was known to have one of the toughest chins in history. He faced some of the most devastating punchers in history and was never knocked down as a professional in 93 fights (his two technical knockout losses came when the referee stopped the fights). In fact in his fight against George Foreman (a man whose punch normally sends mere mortals to the moon), Chuvalo complained to the referee after the fight was stopped.
Though both have become more vulnerable as they've aged, Mark Hunt and Antonio Rodrigo Nogueira were each known for this. Hunt was known for shrugging off life-threatening strikes as mere annoyances, while Nogueira was known for taking immense amounts of punishment, but still somehow managing to not only survive, but to win.
Bert Trautmann, football (soccer) goalkeeper active in the 1950s. During the 1956 FA Cup Final, he was injured in a collision with an opponent. With 17 minutes to go, and no substitutes allowed, he shook off the injury and continued. He saved several goals, preserving his team's lead and helping to win the match. The injury? Merely a broken neck.
Jack Youngblood played the entire 1979 playoffs and Super Bowl, AND the meaningless Pro Bowl game with a broken tibula. Because of this, he was called “the John Wayne of football”.
Steve Yzerman played on essentially on one leg due to having a blown out right knee during the 2002 Stanley Cup playoffs.
Donovan McNabb played on a broken ankle for most of a 2002 regular season game.
Fedor Emilianenko vs. Kevin Randleman. Fedor got hit with possibly the most perfect suplex in history, impacting the mat with all of his own weight plus all of Randleman's weight directly onto his spinal column. He calmly turned around and made Randleman tap out.
O-Chul from The Order of the Stick has survived being in an exploding castle whilst paralyzed, fighting a shark in a tank of acid, and (offscreen) having a staring contest with a basilisk. Word Of God states that he has a constitution score in the mid twenties. The villains have taken to placing him in psychotically dangerous situations simply to bet on his survival. This is a man who has Chuck Norris jerky for breakfast.
O-Chul: [This is] Xykon's spell list. Or most of it, anyway. Roy: Are you kidding?!? How did you get this?? O-Chul: One saving throw at a time.
Bun-Bun has shrugged off attacks that would kill an ordinary human being, made all the more impressive by the fact that he's a rabbit. At one point he was actually eaten alive by an alien, and simply burst his way out of the alien's stomach and proceeded to kick its butt. Bun-Bun has an origin even he is not clear about; he was bought from a Magical Store.
Oasis might also count. She's been through many No One Could Survive That moments, including two explosions and a sniper bullet to the head. How she does this is not yet explained, and may or may not be a superpower she was given by Dr. Steve. Her "sister" Kusari has also survived being stabbed through the chest and even decapitated, again by means unexplained.
The entire cast of 8-Bit Theater has exhibited this despite not having any apparent magical protection.
Fighter himself has survived several stabs to the back of the head courtesy of black mage and it isn't likely he's ever felt a thing. Hell, he even had one used as a lightning rod to channel a Lightning Spell directly into his brain. That particular spell actually INCREASED his intelligence instead of dealing any damage whatsoever!
And coming completely out of left field is quiet, unassuming, Mauve Shirt Airman Third Class Axel Higgs. He gets slammed into a stone wall hard enough to leave a man-shaped dent, brushes it off, then cuts the insane clank that did the slamming with a wrench in a single swipe. Although we're starting to get hints that he's not quite what he seems...
Homestuck: Recently, Gamzee received several hundred bullets in the chest courtesy of Caliborn, and doesn't even stop smiling. Apparently, clowns in Homestuck are death-proof.
Ms. Jones from Gunnerkrigg Court. Trick one: a sword bounces from her face. Trick two: place a palm on a wall. Close the fist, excavating what concrete happened to fit under the fingers. Who she is wasn't revealed yet, only that she's not a robot and probably not a "normal" magic-user either. We already saw one god and one valkyrie at the Court, though... And remember, androids aren't robots, and golems don't count as robots either.
VG Cats parodied this with (amusingly enough, considering the Trope Picture) Zoro from One Piece. Zoro blows off some physical damage taken by earlier attacks... only for Chopper to tell him that he's taken such internal damage from the attacks that most of his colon has to be removed.
Richard in Looking for Group may qualify as a double subversion, given the huge number of Amusing Injuries he's survived with little ill effect. At first it seemed justified by the fact that he's undead, but recently some strips have dropped hints that he may be a flesh-and-blood human masquerading as an undead.
Triple subversion! His immortality is derived from some sort of magic which requires him to kill innocents and harvest their ashes.
Among other things, Vane Black of Next Town Over has been shot through the hand and hanged, and the strongest reaction she has is frustration that John Henry Hunter is getting away because of such holdups.
Jacob Starr of Survival of the Fittest is (in)famous for this trope, to the point of handlers referring to its use as "The Jacob Treatment". The character in question, over the course of his tenure on the island, was hit by arrows, burned, shot, cut and stabbed, all without seeming to flinch or even lose any mobility.
V3's Rick Holeman also took an absurd amount of injuries before dying. These included getting shot in the chest while still being able to run right over to his attacker, knock her over and starting to beat her down. All the while being stabbed with a knife - then he survived long enough to deliver some last words before finally kicking the bucket.
Justified in Broken Saints: Gabriel, The Dragon, can handle the pain of his spear wound so easily because he been genetically engineered to have enhanced physical endurance, among other attributes.
Usually averted in the Whateley Universe, even if it is a comic book universe. Even the Nigh Invulnerable characters get injured. Lancer is a Flying Brick, and in his combat final, he got a dislocated shoulder that sent him to the hospital. He still won, though. Phase seems to be in dire need of her roommate's healing salves on a regular basis.
Randall Octagonapus of The Lazer Collection 3 survives falling from the roof of a tall building and with no reaction other than "Ugh... I'm fine... but this is personal."
The most obvious example from the Global Guardians PBEM Universe would be The Shield, whose only superpower was a complete and total immunity to being injured. It didn't matter what you used on him... his power would let him survive it uninjured. Bullets? He laughed at bullets. Drowning? Sorry, can't drown, though he doesn't quite breathe water in those circumstances. Having a skyscraper collapse on top of him? Granted, he'd get bored waiting for you to dig him out, but in the meantime he'd be fine. Exposure to vacuum? Doesn't faze him. Drop him to the ground from orbit? Been there, done that.
The superheroic Stuntman from the same setting is an interesting variation. His powers revolve around luck rather than simply being immune to injury, so as a result he gets banged up all the time... but never as badly as he should be. Stuntman once was thrown from the roof of a twelve story building, and through a series of lucky breaks and coincidental events managed to walk away from it with a skinned knee and a twisted ankle.
Infinity is amazingly hard to hurt as well because of her mutation. Her bones are made of metal and her musculature is far more dense than normal flesh. She gets hurt all the time, but it takes a lot to do it.
Anvil is literally Made of Iron. Imagine Colossus of the X-Men, except permanently transformed and iron instead of steel.
In Worm, Skitter. Her sheer toughness is demonstrated on several occasions, but the most vivid demonstration comes in 19.2 when she walks up to a hero who uses his power to sort-of cure her, a power which as a side effect transfers her injuries to him. She was prepared to fight without healing, but Tattletale convinces her to go through with it anyway. Afterwards, the hero needs the help of two people just to stand.