In my opinion the biggest secret is that Severus Snape is good.
There is no secret blood relative of Harry's revealed in Harry Potter and the Deathly Hallows.
The order of the Pheonix
Their is no Harry Potter and the DA. DA is a term used by some of Harry's classmates to refer to Dumbledore's Army, the secret organization, run by Harry to teach the students Defence Against the Dark Arts. This club is formed in Harry Potter and the Order of the Phoenix. Harry is 15 in this book/movie and therefor to young to get married even if he wanted to at the time.
Please see the following walk through for details on the secret areas. http://www.gamefaqs.com/pc/562014-harry-potter-and-the-chamber-of-secrets/faqs/55157
Harry, Ron and Hermione refer to him as Snuffles in letters and public conversations.
There is no secret blood relative of Harry's revealed in Harry Potter and the Deathly Hallows.
a sword
Secret!! :p
get married and have 3 kids
He is a werewolf, and that he was best friends with Sirius Black and Harry's dad (James Potter).
Harry opened the secret passage with Parseltongue.
The order of the Pheonix
He knows a lot of secret things in Hogwarts.
The main secret in Harry Potter and the Philosopher's Stone was that the philosopher's stone was being hidden in Hogwarts to protect it.
Harry Potter is set in a whole new secret world which in Britain. Twilight is set in a town in America.
Yes it does it will be coming out June 16,2011
The secret codes are: level5 & level6. :) (No capitals or gaps)