They say that if you hit anyone just right, they'll go down. For the most part, they're correct, but there are some exceptions to the rule.
This is a list of the most iron, granite, and diamond-chinned competitors in MMA, people who will fight through face-disfiguring punishment to continue fighting in the face of defeat.
This is a modern list, so previous top names like Mark Hunt and Kazuyuki Fujita are omitted from this list, with both of them being KO'd recently and looking horrendous while being so.
10. Anderson "The Spider" Silva
"Rich's punches come from weird angles—like you see that?"
Another case that maybe isn't as easy to judge as the others, due to the fact that he's never really been on the wrong end of a beating. Credit goes to his supreme footwork and masterful head movement for this; they allow him to avoid shots and minimise their impact when they land.
But any time he's been hit, he's shaken it off like nothing. Never KO'd or TKO'd, Silva's only losses come from submission, decision or disqualification.
When he got hit by Franklin, he started dancing like Neo in The Matrix (Neo=Mr. Anderson, get it?), and when he got hit by a right hook from Henderson he only beckoned for more.
In clips of him sparring against Antonio Rodrigo Nogueira, he does not wear headgear, and is none the worse for wear for it. Currently sporting a nine fight winning streak in UFC's middleweight division—the highest ever in UFC history—and holding the middleweight belt, my guess is we won't see Silva rocked in his MMA career. But we may if he gets to box Roy Jones Junior.
9. Dan "Hendo" Henderson
"Rich Franklin is pouring it on, here."
With not a single KO or TKO loss of any kind to mar his record, no list of great chins could ever omit Dan Henderson. Even against the calibre of opponents like Rampage Jackson, Wanderlei Silva x2, Anderson Silva, and Vitor Belfort, Henderson's chin held up when going toe to toe.
At 39 years old this August, Henderson is still one of the toughest men there is, and he is poised to get another UFC middleweight title shot should he defeat Michael Bisping at UFC 100.
The only reason he isn't higher on the list is because he has been dropped, notably against Anderson Silva and very badly by Wanderlei Silva early on in his career.
8. Jon Fitch
"Oh, big right hand!"
What Fitch endured against Georges St. Pierre at UFC 87 was not a one-sided fight, or even a one-sided beatdown, it was a massacre, plain and simple, up there with Fedor/Herring or Sakuraba/Arona.
St. Pierre said Fitch reminded him of the Terminator, and it's easy to see why; every time GSP knocked him down, he kept getting back up, and kept pushing forward, unafraid and never giving up.
After suffering that loss, fans often forget that this is still the number two or three welterweight in the world, as often happens when a good fighter meets a great one.
People forget that Fitch had been on an eight fight win streak in UFC before meeting St. Pierre, the joint largest before Anderson Silva defeated Thales Leites last April.
Fitch will look to get back in action at UFC 100 against newcomer and heavy underdog Paulo Thiago.
Having only been stopped once by a knee from Wilson Gouveia seven years ago, Fitch has been finished only once.
7. Antonio Rodrigo "Minotauro" Nogueira
"Beautiful step in, with the uppercut."
Some might wonder why Nogueira is not higher, but after being dropped five times in his last three fights, he can no longer absorb the damage he once could.
Even still, he was pretty much a punching bag for two rounds before getting the guillotine when he fought Sylvia, the kick by Herring was bang on the jaw, and he did get up both times when he was knocked down by Mir and was struggling to his feet when Herb Dean called TKO.
We probably won't ever again see Nogueira come from behind from things like the Sapp piledriver or Cro Cop's left high kicks to get the submission win, but even still, he will be one of the most difficult people in the heavyweight division to finish.
He will face Randy Couture at UFC 102, where if he wins he could be in line for another title shot against whoever the heavyweight champion is at the time.
6. Patrick "The Predator" Coté
"And here we see the laser beam precision of Anderson Silva's punches and the terrific chin of Patrick Coté."
One of the most underrated chins in the sport, Coté took some humongous shots from Anderson without going down once, including a flush head-kick, and brutal jumping knee and a flying punch. His response was a smile or applause.
He's never been KO'd, or knocked down, and has gone toe to toe with heavy hitters like fellow iron jawed competitor Chris Leben and Drew McFedries.
The only time he stopped was when his knee blew against Anderson Silva, an injury that kept him sidelined until this September when he will face Yushin Okami at UFC 103—at least if their verbal agreement is anything to go by.
5. Heath "The Texas Crazy Horse" Herring
"Herring goes spinning back!"
No matter how bad it gets, Heath Herring will still hang in there. The most obvious examples of Herring's never give up mentality can date all the way back to 2002, when he fought Fedor Emelianenko, entering as considerable favourite.
Herring just got straight up brutalised for eight of the first 10 minutes, getting taken down at will—even being suplexed—and punched and kneed until Fedor punched himself out, and Herring managed to get side control and land some harmless knees into Fedor's armpit.
At that point, the doctors decided to call a halt, stating that Herring had received too much damage and Fedor was awarded the TKO.
In his next fight, Herring faced Mirko Cro Cop and was summarily dispatched, being beaten to the punch every time and being finished by a liver kick with ground and pound in just three minutes and 17 seconds of round one.
More recently, Heath Herring faced newcomer Brock Lesnar, who had a considerable size, weight and reach advantage over the Texan, but even then he had to have expected much better.
Lesnar broke Herring's orbital bone with the first punch he threw, sending Herring tumbling backwards head over heels in the process. Lesnar controlled him for the remainder of the fight, punishing him with punches and vicious knees to the body that had Heath passing blood the next day.
Herring has a total of four TKO's on his record, Ramazan Mezhidov (Cut), Fedor Emelianenko (Doctor Stoppage), Mirko 'Cro Cop' Filipovic (Kick to the body and punches) and Sam Greco (Knee Injury).
4. Mauricio "Shogun" Rua
"He's rocked him! Nogueira rocks Shogun but he gets right back up to his feet!"
With a chin that is sometimes forgotten due to his Jiu Jitsu and Muay Thai, Shogun has only been dropped once, and that was against an awesome right hook from Antonio Rogerio Nogueira in the picture above.
He hasn't really been on the end of too many beatings, so the Rogerio punch is the best thing we have to go on, but that was as hard a shot as any ever in the light heavyweight division, and it connected flush on the side of the jaw, and it knocked him down for a total of half a second.
He has been TKO'd once, when he broke his arm after improperly bracing a takedown against Mark Coleman in PRIDE 31, 2006. He has never been knocked unconscious or anywhere near it.
Shogun will get a chance to exhibit his iron jaw at UFC 104 against undefeated Lyoto Machida for the UFC light heavyweight title.
3. Fedor "The Last Emperor" Emelianenko
"Oooh. Oh! OHH! OOOOH MY GOOOD!!!!"
This one is a difficult choice, simply because Fedor is so rarely hit. Even the Randleplex, while undoubtedly the best suplex ever in MMA, didn't seem to hit him properly, instead only hitting the upper part of his back/shoulders and transferring barely any of the force to his skull.
Thus, the only real thing we have to go on is Kazuyuki Fujita's monster overhand right that blasted the Last Emperor on the left temple, causing his legs to wobble and almost give way.
But give way he did not, instead he clinched with Fujita and stopped him doing any more damage. After a brief period on his back, Fedor finished Fujita two minutes later with a liver kick, a left-right combo on Fujita's jaw and finished him with a windpipe choke.
The only TKO on Fedor's record comes via doctor stoppage from an elbow delivered by Tsuyoshi Kohsaka in 2000, reopening the cut that Ricardo Arona had been responsible for earlier that night. He has never been KO'd or knocked down in his 32 fight career.
2. Aleksander Emelianenko
"Now Khaitonov's picking apart Emelianenko."
Another granite jaw, Aleksander, the lesser known of the Emelianenko brothers, has taken the best shots from the best fighters. He has only been knocked down twice in his entire career.
The first was when Aleksander went toe to toe with Sergei Kharitonov, hard hitting boxing silver medalist in the 2003 Central Asian Games, for the entire fight.
He was having huge trouble early on, losing the striking convincingly, and even getting dropped, but after a round of being teed up on, Aleks came back with a couple of power shots and finished Kharitonov with knees to get the TKO at 6:45 of the first round.
The second was Aleksander's first and only KO, from a Cro Cop left high kick to the jaw followed up by hammerfists, but even then he still clung to consciousness. His large frame, great chin and fast and powerful boxing makes Aleksander one of the most talented people in the heavyweight division. That is the only (T)KO on his record to date.
However, with no big fights lined up and not currently ranked in the top-10 by anyone, I'll agree with his big brother who believes he wasted his natural talent.
1. Quinton "Rampage" Jackson
"How is Quinton Jackson still standing?"
No list could be complete without Rampage Jackson. Jackson has two TKO's and one KO on his record.
The TKO's came from Mauricio Rua, who broke his ribs and used the Muay Thai clinch to deliver a series of debilitating knees to Jackson's head, before finally soccer kicking him in the head to get the TKO, and from Wanderlei Silva, who used the Muay Thai clinch to deliver about 13 unanswered knees to Jackson's skull, before he finally collapsed in a heap, leaving the referee to call the stoppage.
He had a close call against Ricardo Arona, looking like he was out for a second after eating a few upkicks, but his only true KO was a horrific one.
Wanderlei Silva started it off with a gigantic right hook, the shock of which could be seen running down Silva's bicep, and once again, Silva used the clinch to deliver a series of knees, and did not stop until Jackson went completely limp, falling through the ropes with blood dropping from his mouth.
It was one of those KOs where you have to wonder if the KO'd fighter would ever come back as strong, but that he did, winning the UFC light heavyweight belt from Chuck Liddell in his second fight with UFC.
He lost in in his first title defense against Forrest Griffin, but with a vengeful knockout of Wanderlei Silva last December, he is poised to fight Rashad Evans for a title shot against Lyoto Machida.
Honorable Mentions: Chris Leben, BJ Penn, Takanori Gomi, Tim Sylvia, Mark Hunt, Kazuyuki Fujita, Nick Diaz, Kiril Sidelnikov.