Rogal Dorn
Rogal Dorn is the Primarch of the Imperial Fists Chapter, which was a Legion before Horus fucked everything up. He is also regarded as being kind of an asshole towards his siblings. He's also the 40k Abraham Lincoln because he has a bitchin' moustache and can't tell a lie.
The Imperial Fists are quite famous for fortifying the shit out of everything and INTENSE CAMPING which pisses off every other race. They are highly likely the reason that the Emprah didn't get raped by Horus during a certain (totally awesome) siege. His evil twin/Brother is Perturabo, Primarch of the Iron Warriors, who turned to Chaos because he was one of Horus's ass slaves. Rogal and Perturabo had an intense rivalry which led to old Petty Perturabo hating him. Fulgrim asked Dorn if he could build a fortress which Perturabo couldn't crack. Dorn is brutally honest, so he just said, "Yes.", well that royally pissed off Pert. Despite what lovers of Perturabo say, Dorn wasn't boastful, seeing as the only fluff that says this is either from Pert's point of view or coming from the mouth of someone who's being a kiss-ass to him. He also had problems with Corax, Curze, Alpharius, and.... Really anyone who wasn't the Lion, Sanguinius, Horus, Leman or Guilliman. In the case of Alpharius, him and Guilliman being a pair of giant assholes is what eventually led to Alpharius saying "fuck that" and signing up with Horus.
During the Siege of Terra, Rogal went with the Emprah and Sanguinius to Horus's battle barge to face the traitor. When the Emprah totally fucked up Horus, Rogal seemingly came out of nowhere and saved his ass, then got all pissy about it because he was only a few seconds short, and found Sanguinius dead and the Emprah dying. Surprisingly, he did not turn into an Angry Marine, but still whines about it like some emo bitch who can't move on, which Corax purportedly found painfully ironic.
When Roboute Guilliman showed off the Codex Astartes and demanded that the Space Marine Legions break up into Chapters, Dorn led the opposition against it, and only submitted after those cowards opened fire on his fleet, deciding that tradition really wasn't worth starting another civil war over. Though it does pose the question of how he prevented his fleet from returning fire thinking those shooting were traitors (which everyone would shoot) and got the other guys to stop shooting at him. In fact, I'm pretty sure that Guilliman himself would have ordered his ships to fire on the idiots who shot at his loyal brother. To say nothing of the other pissed primarchs. Then there is the question of why the legions couldn't have broken down their existing system. You know: ten, one thousand strong Chapters per Great Company, ten Great Companies per Grand Battalion, or something like that. Then they would simply need to maintain close contact between Chapters and Companies and Battalions and insure that the leader of a Chapter commands those directly under him, the leader of a Great Company commands only the Chapter Masters (with little-to-no control over the marines of those Chapters, just general authority), and so on up the chain of command to the primarch (who should have a Prefectus like the Romans did as a second-in-command, just in case). FYI, this structure already existed (except they were not always called Chapters, it varied between Legions). Idiots.
Much later, after the Second Founding, he declared to everyone that he'd capture his nemesis, Perturabo, inside a metal cage. Pert then trolled Dorn by setting up the "Eternal Fortress", which was fortification after fortification that led into a fortress that Perturabo was residing in. It took the Imperial Fists three weeks to wade through the shit Perturabo set up. However, it was too late for Dorn to realize that he has just been trolled by Pert. When his Imperial Fist strike force reached the actual fortress, it was actually empty - a giant, centrally-open kill-zone with virtually no cover - and with the Iron Warriors waiting in ambush. Suffice to say, the Imperial Fists then got their asses handed to them, and wound up having to use their fallen brethren for cover up until the Ultrasmurfs came in and rescued them. By the time they escaped the planet, the casualties that the Fists had taken were enormous. To their credit, they still managed to give the Iron Warriors so much trouble that wiping the Fists out completely would have required them to sacrifice most of their own legion, including Perturabo himself. Or at least Imperial Fists themself say so. Not like Pert give a single shit about it - entire point of Iron Cage trolling was to humiliate Dorn and his legion, not to kill them.
Soon after this, Rogal got in a big-ass ship and got pwned by Angron in the first Black Crusade, (he did manage to wreck the whole damn crusade though) therefore proving that RAGE ends all things and how Angron is among the only Chaos Primarchs that actually gets anything done these days (yet his Primarch kill count is 0. hmmm.) During this battle, Rogal boarded one of the ships and was swarmed and killed by an unholy amount of traitor marines. So the story goes anyway.
Fun fact: Black Watch RPG rulebook have a quote of Rogal Dorn, dating M40. Is this a typo, or golden boy just fake his death and now rule Custodes operations, like some rumors claim?
The whole 'died in a zerg rush of world eaters' doesn't make much sense anyway.. If it was supposed to be Angron who killed Dorn, maybe that'd make sense. But just a pack of marines? That's... Less likely, if only because it's unlikely that there actually were enough World Eaters left to pose any real threat to a primarch. Before Istvaan there was something like 150,000 World Eaters, but they took big casualties, first on Istvaan III in their unsupported attacks on the loyalists, and losses again on Istvaan V, then AGAIN on Nuceria and one last time outside Big E's pimp crib, where Sagnuinius was regretably forced to choke a bitch en masse for a few days. Point is, if Dorn died (as he lived) beating the shit out of people less manly than him, then it was because he wanted to die.
Tabletop
The Emperor's Praetorian allows all Imperial Fists to use his Ld for leadership and pinning tests, while also granting a +d3 bonus to the outcome of assault results for himself and his Legion as long as he's in play. In addition to that, he also makes Phalanx Breacher Squads and Legion Terminator Squads Troop choices and he (along with his squad) has the Crusader and Furious Charge special rules. Sundering Blow acts like a powered-up Smash, halving Dorn's attacks to boost his strength by 2 and giving Instant Death, while Unshakable defense allows you to pick three fortifications to enhance; these fortifications will allow units hiding in them to reroll pinning tests and cover saves of 1. Dorn gets the following wargear: Auric Armor, that gives him a 2+/4++, and no attack that rolls better than a 3+ can wound Rogal Dorn, regardless of any special rules it has. (This doesn't apply to Strength D weapons.). Storm's Teeth is an AP2 melee weapon with Unwieldy, Shred, and Rampage and The Voice of Terra is a S5 AP4 gun with Salvo 3/5 and Rending. Lastly, he gets access (like good old Perturabo) to his own pimped ride, the Aetos Dios, a modified Thunderhawk usable in games of 3000+ points as a dedicated transport. The Aetos Dios is armed with a Turbolaser and also has a single void shield, IWND, and a 4+ invulnerable save against all missile attacks. Like Perturabo's Tormentor, it doesn't take up a Lord of War slot.
| The Primarchs of the Space Marine Legions |
|---|
 Loyalist Corvus Corax - Ferrus Manus - Jaghatai Khan Leman Russ - Lion El'Jonson - Roboute Guilliman Rogal Dorn - Sanguinius - Vulkan |
 Traitor Alpharius/Omegon - Angron - Fulgrim Horus - Konrad Curze/Night Haunter - Lorgar Magnus the Red - Mortarion - Perturabo |