The Head of a Navigator
From Monkey Island wiki
The Head of a Navigator (also known as Navigator Head) is an enchanted head of a navigator who was captured by the Monkey Island Cannibals. It has been enchanted so that it always shows which way the carrier must go to reach his destination. Guybrush uses it in the first game to navigate the Caverns of Meat underneath Monkey Island while trying to get to LeChuck's ship.
The Navigator Head is wrapped in a necklace of eyeballs that makes it invisible to ghosts. If the player begs the head enough he will give the necklace to Guybrush. Alternatively Guybrush can instead choose to threaten the Navigator Head. The Head will counter with a threat to strand Guybrush in the Caverns of Meat forever. Guybrush will then counter THAT threat with yet another threat to drop-kick him into the lava. After this the Head relents and lets Guybrush use the necklace.
The Navigator Head seems to have adjusted to his current state with a positive attitude. He even smiles on two occasions. In both negotiation scenarios for the necklace, the Head closes with a relatively positive statement that there isn't much point in having a necklace without having a neck anyway.
In Monkey Island 2: LeChuck's Revenge Captain Dread has lost his lucky amulet, the eye that has seen the world, and refuses to leave Scabb Island without it. The amulet is apparently the only part of his former navigator left back by cannibals (an eyeball). This leads to the natural assumption that the Navigator Head was once Dread's navigator. The Navigator Head does, however, have both eyes, though the cannibals may have replaced one or both.
In Escape From Monkey Island Guybrush can ask the Voodoo Lady for an invisibility necklace, to which she replies "It's been a bad year for unspoiled eyeballs". This is a reference to the necklace made of eyeballs.
