Warriors who fought in a crazed state. 

Berserker
The berserker is closely associated in many respects with the god 
Odhinn. Adam of Bremen in describing the Allfather says, "Wodan --- id est furor" or "Wodan --- that means fury." The name Odhinn derives from the Old Norse *odur*. This is related to the German *wut*, "rage, fury," and to the Gothic *wods*, "possessed" (Georges Dumezil. The Destiny of the Warrior.Chicago, U of Chicago P. 1969. p. 36). This certainly brings to mind the madness associated with the berserker, and other Odhinnic qualities are seen to be possessed by the berserk. Ynglingasaga recounts that Odhinn could shape-shift into the form of a bird, fish, or wild animal (Snorri Sturluson, p. 10). The berserker, too, was often said to change into bestial form, or at least to assume the ferocious qualities of the wolf or bear. Kveldulfr in Egils Saga Skallagrimsonar was spoken of as a shapechanger (Hermann Palsson and Paul Edwards, trans. Egil's Saga. NY: Penguin. 1976. p. 21),and Hrolf's Saga tells of the hero Bjarki, who takes on the shape of a bear in battle: 
 

Men saw that agreat bear went before King Hrolf's men, keeping always near the king. He slew more men with his forepaws than any five of the king's champions. Blades and weapons glanced off him, and he brought down both men and horses in King Hjorvard's forces, and everything which came in his path he crushed to death with his teeth, so that panic and terror swept through King Hjorvard's army..."