Grashkar Gitface was an Ork Warlord in the 41st Millenium who held a small Empire in the Ragnarok system.
Gitface was so named because, prior to ascending to being a Warlord, he was the servant of a Warlord whose name has been unrecorded, who referred to him as "Gitface" for the entirety of their association (i.e: "oi! Gitface!"), until Grashkar killed him, and reclaimed the title for himself. Whether he did this as an act of respect for his former master or hatred of him, no one knows.
He then, after securing the loyalty of his former master's Orks (mainly through judicious - as well as gratuitous - use of stomping, shooting and hacking), led his Orks to claim the worlds of the Ragnarok system (a system near the Eastern Fringe - most Imperial Analysts believe it belonged to the Tau prior to the Orks arival), and carved himself an empire, dominating it with an iron fist.
Once there, he lauched raids at the nearby Imperial Worlds. He became known first as a minor pest, then a major problem, until finally Imperial authorities could take no more of his presence and decided to act. At the High Lord's behest, elements of the Revenants Chapter and three regiments of Imperial Guard were sent to destroy the Empire of Ragnarok. During the final assault, Grashkar, holed up in his palace, fought Yan Rill of the Revenants in single combat; though the Ork was a powerful warrior, fate was with Rill, who broke the Ork Warlord and hurled him from a balcony. With his death, his Orks scattered.