Another word for berserk

Berserk was famed for the reckless fury with which he fought, always going into battle without armour.

The Barbarian excels at melee attacks, is fast and can berserk, but he cannot wear heavy armor without training.

And did I mention that entering Berserk Mode will make you go crazy, just like Guts?

BERSERKER (from the "Sark" or shirt of the "bear," or other animal-skins worn by them), in Scandinavian mythology, the name of the twelve sons of the hero Berserk, grandson of the eight-handed Starkadder and Alfhilde.

Now, the fun comes when it's time to activate Berserk Mode.