The Bat-Bogey Hex is a hex. The incantation is unknown. It is said to grotesquely enlarge the victims snot, give them wings, and send them attacking the victim.
 Known Uses
Ginny Weasley was a noted practitioner of the hex, and used it to good effect on two occasions. The first use was to overpower Draco Malfoy in Dolores Umbridge's office during her tyrannical tenure as Headmistress of Hogwarts, allowing Ginny, her brother Ron, and their companions, Neville Longbottom, and Luna Lovegood, to escape. The second occasion was used on Zacharias Smith, who annoyed Ginny on the Hogwarts Express by asking her exactly what occurred at the Battle of the Department of Mysteries. This use garnered the attention of Horace Slughorn, who invited Ginny to take lunch with him as part of his Slug Club. Ginny may have also used this spell on her brother George, as he once mentioned her skill to Harry Potter.