Halo Cheats - Xbox

Random message
Go to "Settings" at the main menu, then press [Y] to create a new profile. Enter ".fortune" (note the period character) as a name. As soon as you enter the last letter of the name, a strange random message will appear. Every time you enter this name, you will get a different message. ".fortune" is a reference to a feature on the Linux/Unix operating system.

Alternate ending sequence
Successfully complete the last level of the game in campaign mode under the legendary difficulty setting. The new ending features a human and alien fighting hand to hand. The human will say "Its over", and then they hug because they know the explosion will kill them both. Also, the FMV sequence of each battle scene will be slightly longer.

Alternate dialogue
Playing under the legendary difficulty setting introduces new dialogue not heard in other modes. For example, after being massacred by a force of Grunts, Jackals and Elites, one of the grunts asks, "Can I have his helmet?". Also, your fellow Marines seem to be a bit more chatty (as well as profane).

Under the legendary difficulty setting, view the entire first FMV sequence. During the sequence, the General says things very differently when compared to the sequence under the easy difficulty setting.

Final ending scene
Successfully complete the game on any difficulty setting and wait for the credits to end. The game will show the Monitor fly across the screen and laugh.