Berserker

Berserker is a non-canonical Power-Up. It can be obtained like any other Power-Up; by killing a zombie. Berserker is a rare collectable, usually appearing beyond round 15. Berserker allows the player who collected it to have unlimited ammuntion, points, and health for 15 seconds. This can be a life saver on small, enclosed maps such as "Five". The image of Berserker is a straining face full of rage.

Trivia

 * Berserker is a reference to the Call of Duty: World at War death card cheat "Berserker".