Tyrant's Helm

The Tyrant's Helm is a headwear item for Atlas and P-body. It is a metal Viking helmet with two horns on its sides, the left of which is broken. This hat is given to players who own the Tyrant's Helm hat in Team Fortress 2.

Trivia

 * There is currently no evidence that a viking ever wore a horned helmet in combat. There is, however, some evidence that such helmets were used for religious or ceremonial purposes.
 * The desciription of this hat in Team Fortress 2 says: "I kicked your ass so hard it went back in time and got me this VIKING HAT". But the description wouldn't be seen in Portal 2.