2. A vampire master is born.
Harry saves one of the top vampires (vision Voldemort?). The vampire forms a bond with him (guardian bond) and Harry learns more and more of the vampires. Ron is disgusted. Hermione disapproves. Dumbledore tries to get the vampire to leave but because of the bond the vampire has a right to be with Harry and Harry doesn't really mind. Harry and the vampire become friends. Harry is attacked by death eaters in Hogsmeade (make a death eater similar to the 'ghost' of the Cear Azkaban fic only using silver arrows –with poison?- shooting from his wand to disable his enemy) the vampire saves him at the cost of silver poisoning thus dying.
Harry doesn't want any body dying for him after Sirius and uses his wand to try and save him but it is no use. Completely devastated Harry throws away his wand and sobs on the vampire (Harry's wand snapping? Back pocket in his trousers when blown away or knocked over his wand snaps?) due to the extreme emotional turmoil Harry's magic surges forth and uses the guardian bond to heal the vampire turning it into a master bond (!). Harry slumps unconscious on the vampire and magic still flows between the two of them (the black of the vampire and the green of Harry). They are transported to the hospital wing but can not be removed from each other for more than two meters or so.
Harry is now the vampire's master with all the consequences and this changes both Harry and the vampire (the vampire is immune to sunlight and doesn't need to feed so often, Harry gets vampire treats, strength, hearing, endurance, sight, instincts, doesn't need blood but it gives him more power and Harry has power over the vampire, the vampire sire's bond is changed to Harry, the vampire must do what Harry says and is obligated to protect him). Naturally, this has a big impact... Plottwists and insanity rule.