Given the question: Question: What does Harry reveal is a fake Horcrux If there is no answer, please output "Insufficient information to provide an answer.". Movie title: Harry Potter and the Half-Blood Prince Context: Scarred by his experience at the Ministry of Magic with Voldemort, Harry is reluctant to return to Hogwarts. Dumbledore encourages him to continue, after transporting him to see a former professor, Horace Slughorn, hoping that Slughorn would return to Hogwarts and take Harry under his wing.Meanwhile, Death Eaters begin to wreak havoc both towards Muggles, destroying the Millennium Bridge, and Wizards, kidnapping the wandmaker Mr. Ollivander and destroying his Diagon Alley shop. Bellatrix Lestrange entreats Severus Snape to enter an Unbreakable Vow with Draco Malfoy's mother, Narcissa, assuring that he will complete the task assigned to Draco should Draco fail and that he will protect him and make sure he doesn't get hurt. Harry, Ron and Hermione, while in Diagon Alley, spot Draco entering Borgin and Burkes and taking part in a ritual with other Death Eaters, and become suspicious of his actions.At Hogwarts, the school is under tight security to prevent the Death Eaters from entering the school. With Slughorn back to teach Potions, Snape is given Defense Against the Dark Arts. Harry and Ron are encouraged by Professor McGonagall to take up Potions now that Slughorn, with lower standards, is teaching the class; however, as neither was expecting to take the course, they have to find textbooks for themselves in the bookcase. Harry's book is annotated with more exact instructions to complete potions, giving him an edge over the other students; he finds that it once belonged to the "Half-Blood Prince", a term Hermione cannot figure out. Meanwhile, Ron becomes the successful Gryffindor's Quidditch goalie, attracting the love of Lavender Brown, much to Hermione's chagrin. Harry is also upset over Ginny's attraction to Dean Thomas. During the Christmas Break while Harry and Ron are at the Burrow, the Death Eaters with Bellatrix in charge come intending to kidnap Harry, but are forced to retreat after they are outnumbered by Order of the Phoenix members. Before they leave they set fire to the Burrow, and the Weasleys...
The answer is:
A small pendant.