Well, its been a few days since I posted anything because I went back and scoured book #2 again. JKR stated that the 2nd book was almost had the 6th book's name and that many clues regarding book 6 was in book 2. This is my conclusion for what its worth. For those that have said it's Tom Riddle, I really agree with and I will tell you why. Dobby stated that before he became Voldemort he could be named freely (thats because he really didn't exist yet). Dumbledore stated that after Tom left school, he got involved with the "worst of us" & underwent so many dangerous, magical transformations that when he resurfaced as Voldemort, very few even knew who he was once the clever, handsome Head boy here. When Harry went back 50 years in the diary, he saw Tom meeting with the headmaster about staying on at the school during the summer. The headmaster asked if he was muggle born, Tom replied, "Half-blood sir." I don't remember seeing that term used before he used it. There are so many more clues but it makes perfect sense. Book 6, is going to go into more detail about Tom Riddle which will end up shedding a lot more light on why he became Voldemort and why there is such a resemblance between Tom and Harry's early lives, both orphans, half-bloods, etc. This may also clue us in on why he went after Harry instead of Neville. Let me know what you think.