Gorgutz 'Ead 'Unter
Gorgutz 'Ead 'Hunter was an Ork Warlord of the Blood Axes and later Evil Sunz. He was involved in several major campaigns in M41. First was the battle for Lorn V, where he temporarily allied with (and then took the head of) Lord Crull, the World Eaters champion. After being defeated on Lorn V, he fled to Kronus and built up his Waaagh! once more, only to - once again - be defeated. He then arrived in the Kaurava system, settling his forces on Kaurava II, eventually conquering the entire system. Next he was seen on Acheron[Needs Citation]
As his name implies, Gorgutz has a penchant for taking the heads of his enemies, for as he pointed out to one particularly unobservant Nob, it would make no sense to put someone's foot on his "pointy stikk".[Needs Citation]
Gorgutz originated as a simple Warboss on the planet of Lorn V, where various Ork tribes had been warring with each other for untold generations. Here his Waaagh! originated, as he united the tribes of rival Orks under his control, by burning their big banners. One notable tribe he captured were the Footstompas, a group of Orks that trained Squiggoths. Warlord Gortgutz defeated them by sending their own Squiggoths against them.[Needs Citation]
During the campaign of Lorn V, Gorgutz harboured a shaky alliance with Lord Crull, a champion of the World Eaters Chaos Legion, which was eventually broken towards the end of the campaign. In the midst of an Imperial Guard invasion supported by Eldar, Gortgutz eviscerated his one-time ally, claiming the Chaos Lord's head for his own. Gorgutz then beat a hasty retreat to build up his Waaagh! after defeat at the hands of General Sturnn.
Gorgutz eventually resurfaced once more, this time on the Necron Tomb World of Kronus. Here he led another bloody Waaagh!, which, although it once again ended in his defeat, the infamous Warlord escaped once more, with many more skullz on his pointy stikk.
Gorgutz returned for one another slaughter at Kaurava II - there were many Feral Orks there, and no greenskin should be fighting without him as far as he was concerned. When he formed his new Waaagh!, he switched allegiace from the Blood Axes, to the Evil Sunz. He ultimately conquers the system and transforms it into a staging point for his WAAAAGH!, beginning a campaign of galactic conquest. 
Gorgutz again returned on the world of Acheron, seeking the Spear of Khaine. After clashing with Biel-Tan and the Blood Ravens under Gabriel Angelos, Gorgutz is forced into a temporary alliance with his foes in the face of Daemonic forces. The Blood Ravens eventually destroy the world to prevent the Daemons from spreading, but Gorgutz is teleported to safety. Gorgutz is nonetheless able to acquire the spear as a trophy before leaving.
He is the second longest appearing character in the Dawn of War series (the first being Gabriel Angelos) having appeared in Winter Assault, Dark Crusade and Soulstorm without dying and has made a return in Warhammer 40,000: Dawn of War III.
A Warboss named Gorgutz appears in the graphic novel Blood and Thunder, but that warboss is killed in the third chapter of that series, so the character detailed above is likely to be a different Ork.