In the latest edition of Famitsu, a popular gaming magazine in Japan, there were pictures of the 'Legendary' edition of Halo 3. This is basically just a version for hardcore Halo fans out there.
In the picture, it appears that there is a well built case, as well as Master Chief's helmet. We don't know exactly how it is going to work though, whether or not stores will just hand out the helmet and the the case to go with it. More likely than not, the helmet will go over the game and case, and they will attach somehow.
Also, Gamestop has commenced taking pre-orders on the game. The release date that they are stating is November, 2007. To pre-order the game, you have to pay $5 as a pre-order fee. That is just for the basic game. To get the collectors edition of the game, you have to lay down $10, and the 'Legendary' edition, as shown above, you have to put down $25. With a pre-order price of $25 dollars, you can be assured that the game will not be cheap. It could cost up to $100.