Grimskull

You'll both love and hate this four-eyed bastard.

"I'm Boss GrimSkull ! This whole planet is mine !"

Grimskull was the Ork Warboss leading the Ork WAAAGH! invading Graia and the secondary villain of the game Warhammer 40,000: Space Marine. He is also nigh imposssible to kill; not even bloodletters can, and those things kill as a hobby.

Graia

Grimskull led his Waaagh! to Graia with the intent of looting the Forge World's Titans. Whilst in his cruiser, he encountered Captain Titus (who had used a jump pack to board it). Whilst trying to fill the Ultramarine's body with lead, Titus used the cruiser's cannon to destroy the bridge, making the cruiser crash land. Grimskull, however, managed to survive.

Grimskull encountered Titus again in Manufactorum Ajakis. While Titus was trying to get the mysterious power source, Grimskull (who was attacking them), became interested in it and sought to claim it as his. However, the power source became unstable and exploded, which sent Titus plummeting to the sewers. Rather annoyed by this, Grimskull sent his Orks to retrieve it. They, however, failed.

As Titus tried to activate the Psychic Scourge (a weapon that was apparently capable of destroying the Ork invaders), Grimskull arrives by dropship. As Grimskull was about to attack, he gets blasted by psychic waves. However, to the Ultramarines surprise, this didn't actually kill the Orks, but instead opens warp portals that allowed the Forces of Chaos to enter the forge world. After getting back up his feet, Grimskull was then swarmed by bloodletters, which made him lose his footing and fell off the railings. Whilst Titus and the group were being incapacitated by the Chaos Lord Nemeroth, Grimskull managed to climb back up, apparently defeating the bloodletters without such as a scratch on him, and engage Nemeroth in combat after saying the most badass thing an Ork has said in the game 'I ain't so Easy to Kill', but got his ass kicked after a short fight which ended with Nemeroth pushing him off the platform, but Grimskull managed to grab hold of him pull him down with him.

Grimskull made his final appearance trying to kill Titus; however, the Ork was bested by the Ultramarine and got his face blown off by a plasma/bolt pistol shot (depending on which of the two Titus has equipped at the time). Without their boss' leadership, the Ork horde quickly fell into disarray. Leaving only the Forces of Chaos for the Imperial Forces to deal with.

Trivia

• His coloring suggests that he's from the Evil Sunz, which explains his deep-seated desire for lootin'. If they won, you know that "mysterious power source" would have ended up being the engine in his sick new buggy.
• He is one of the rare kind of Orks, since he actually has a bit of tactical awareness. This is shown when he orders his Orks to seize the planetary defense weapons and turn them on the Imperial ships, denying the Imperial ground troops any further support. Titus even remarked that he wasn't a fool, which is about on par for a Warboss.
• He is one of the very few Orks who can actually hit his target.
• Titus is finished with him.
• He and the Orks depicted in Space Marine are apparently less grammatically challenged than the Orks usually depicted in other games (possibly a side effect of their leader being no fool).
• He's the only character to have a more traditional boss fight. Unlike Nemeroth, whose boss fight only consisted of really easy quick time events.
• His Mega Armour is powered by a totally badass V8, mounted on his back. It's also manly as all fuck because its only the arms and backpack. (It's also not Mega Armor; Grimskull uses his V8 Engine only for murder, leaving the rest of his body to tank plasma bolts. Take a look at him, he doesn't cover his green with metal, because that would take away from the Ork underneath)
• His WAAAGH and him go out of their way to show Orks aren't all comedic relief like they are in other games, and the message you find is actually quite dark: We're talking multilated bodies of innocents filling bloodsoaked halls and workers wards, which Titus notes Orks do "for sport".
• He's fucking awesome.
• He shares his name with a Space Wolf from the Ragnar Blackmane books, but they've never met.
• And last but perhaps most importantly of all...He ain't so easy to kill

Quotes

SPACE MARINE! WAZ DAT SAPOSSED TA HURT? ARHARHARHARH!