Many characters in Frank Miller's Sin City exhibit this trait to an incredible degree. Made of Iron is probably Miller's all-time favorite character trope for male protagonists. He just loves guys who can take an appalling level of punishment from vastly superior opponents through force of will, strength of character, or just innate badassery.
Two characters who seem particularly adept at shrugging off damage are Manute and Marv, who require really extreme trauma to be eventually killed: Manute in a hail of bullets courtesy of an army of prostitutes; Marv by being electrocuted in the electric chair - although notably, Marv doesn't die until the second time in a row he's electrocuted.
Marv: Is that the best you can do, you pansies?
The animalistic Kevin is so good at avoiding damage that he doesn't get a chance to display his durability much, but the fact that he can survive being dismembered, eaten alive by a wolf, and eventually disemboweled, without even making a sound, until he's finally killed by decapitation indicates that he's got a lot of iron in him as well.
Quite a few characters from The Bad Eggs manage to survive seemingly fatal incidents. Ript is eviscerated and later stomped on by a Brontosaurus (in the same issue, no less), and neither of these injuries seriously damages him.
The more recent comic books (i.e. Hush) tend to show Batman's upper body as pretty much a mass of scar tissue by this point.
Cassandra Cain is at least as bad about this. She usually gets out of the way, but when obliged to take a bullet she can do so and not even flinch. It's mainly practice.
Robin: Are those... exit wounds? But they're so big. Batgirl: I... grew.
Subverted to tragic effect in an issue of ElfQuest, where a couple of boys from a human tribe throw a stone from a sling to knock an elf off of a high tree branch, believing that elves are indestructible. They're not. The elf breaks his back. The elves do have magical healers, but the injured elf is found and killed by the boys' grown-up relatives.
It remains to be seen what future authors will do with the character in terms of this, since Ennis is leaving the character after eight years, his current story arc being the final one, and other writers have already started. In the two thus far published stories, the Punisher MAX Annual #1 and Punisher MAX: Force of Nature, he doesn't take so much damage as to invoke this trope.
In one of the Ennis' The Punisher MAX stories Frank takes a shotgun blast to the side that removes a big chunk, including an entire rib bone. One would expect Frank to stumble off and let himself heal in the manner that an extremely well-trained and diligent former Marine would do. But with the shotgun wound, Frank continues to fight on... not even bleeding. In the same story The Dragon gets impaled, shot, beaten, further impaled, his face quite literally blown off and lives several moments past that, before finally snuffing it.
It's implied in The Punisher: Born that Castle's near-inhuman ability to survive damage that would kill anyone else is that he made an unconscious pact with death during The Vietnam War that would let him continue to fight a war that never ended - for a price.
Both Nick Fury and Tony Stark keep extensive files on all known superhumans, and it's a indication of how dangerous they consider him to be in that both of them keep a file on the Punisher. In addition, they each make a point of commenting that Frank has a nearly psychopathic ability to tolerate pain.
In Jason Aaron's Punisher MAX run, the continuation of Ennis' run, Frank's years of injuries are finally starting to catch up to him. A doctor flat out tells him that his body is a wreck and will only get worse. However, in the same series Frank takes an extraordinary amount of damage. In one night he gets stabbed several times with a sai (including one through his forearm) and takes several gunshots (including one self-inflicted one through the left chest-shoulder area to hit someone behind him). Then he walks across town and is met with no less than six more gunshots, gets his head smashed both through a car window and against a fire hydrant. He remains conscious long enough to walk back into the city then back into the suburbs before passing out. The trope is ultimate averted when Frank succumbs to his injuries.
And OH GOD, all the shit it took to kill Max!Bullseye, The Mennonite and Barracuda, think Pittsy, The Dragon mentioned above, times five. And The Mennonite was a Amish guy! Okay, he used to be a mob enforcer before turning Amish, but still!
X-Men subteam The New Mutants. Roberto DaCosta has super-strength, but not super-durability. He's explicitly just as vulnerable as any Joe SixPack... but somehow still survives nonsense like getting tackled through a brick wall. A degree of superhuman durability is pretty much a Required Secondary Power for any character possessing superhuman strength, as super-durable muscle fibers would necessarily result in super-durable muscle tissue, protecting most everything but the eyes.
V: Did you think to kill me? There's no flesh and blood within this cloak to kill. There's only an idea. Ideas are bullet-proof.
Tallulah Black from Jonah Hex has survived things like being shot in the head, being horribly mutilated, and having a baby cut out of her. And of course, Hex himself has gone through all of the above (except the last bit) and more many times, and with only 19th century frontier medicine (sometimes!) available to bring him back.
Sgt. Rock often takes a hell of a beating. This trope also applies, unsurprisingly, to his Arch-Enemy, "The Iron Major".
Taskmaster. Neither getting rammed by a speeding car, nor shot repeatedly, nor being kicked in the face by an enraged Spider-Man so hard that his body punches an economy-sized hole through the (in all likelihood heavily armoured) wall of the armoury in his hideout/gym will do more than slow him down momentarily.
They have fallen in concrete pools that have solidified with them still submerged on it.
They have been put under objects that were very heavy (as in, the range of metric tons).
They have been thrown to outer space with no space suit whatsoever.
They have been devoured whole by different wild animals, mainly lions and giant snakes. They sometimes cry for help from the beast's stomachs.
Mortadelo:(after being rescued by Filemón when a bird attempted to eat him while he was in an insect disguise) What a dreadful experience, boss! I've seen its esophagus, its craw and its sternum... from inside!
Once they broke an old fortune-teller's crystal ball... which prompted the old fortuneteller to reveal she was actually a buff thug in disguise. Cue Mortadelo and Filemón on their graves on a graveyard, apparently alive ("How are you doing, boss?" "Meh, kinda chilly in here.) After escaping their graves, Filemón tellsthe reader "You don't want to know how we did this." On the background we see an archangel chiding St. Bartholomew "I don't care if you're a fan of Mortadelo! The rules are clear; no miracles!"
Lampshaded by Mortadelo on "¡Elecciones!" after falling off the building when trying to get into Ofelia's apartment to investigate her:
Come on, boss, it was just an 11th floor! We've been through worse!
Kick-Ass. Hand Waved by his dulled nerve endings but that fails to explain how he shrugs off the damage from repeated electric shocks and multiple beatings without requiring a lick of medical attention. The various pins and metal plates he got after the car accident would account for some of his resistance to injury, though this has clearly been turned Up to Eleven.
Despite all the punishment that The Fox goes through, outside of a black eye here and a bruise there, Paul Patton Jr. never really seems to be the worse for wear. Mind you, he doesn't even have superpowers.