Anteoculatia is a hex that causes the target to grow antlers.
Gilbert Wimple from the Committee on Experimental Charms presumably had this spell used on him, as he had large horns growing from his head before the 1994 Quidditch World Cup.
In 1996, after Fred and George Weasley's dramatic exit from Hogwarts, Pansy Parkinson was hit with this spell, presumably in retaliation for the fact that she and other members of the Inquisitorial Squad had been helping Argus Filch to crack down on the sudden increase in rule-breaking. The next day, Pansy had to miss all of her classes, which pleased Hermione Granger.
Behind the scenes
This spell was briefly mentioned on question seven of the WOMBAT Test on what should receive the lightest punishment by the Wizengamot as "horns created on a culprit's mother by a broken wand".