Romero's head

This thing looks like John Romero's head on a stick. You have to shoot it with the rocket launcher in Doom II MAP30: Icon of Sin or you can be a big fat cheater and noclip yourself and shoot (or punch or saw) the head.

The head has about the same health as a cacodemon, but each rocket will only do a little damage, so it takes 3+ rockets to kill the head. When the head dies, there are explosions and the level ends.

The head alone is harmless, but usually with these heads come spawn shooters.

Romero's head has a sprite prefix of BBRN, and is also known as the Boss Brain. This is an insider joke: the "boss brain" of the level is the head of one of the bosses of id Software.