Halo

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.
halo.bungie.org via Doggone and Brent Couch.

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

Alternate ending sequence:
Complete the final 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.
Nathan Benton and Boyoben.

Alternate dialogue:
Playing under the legendary difficulty setting will introduce 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).
Eric Redmond.

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.
onuhat tweigm bipareeMuhammad Akhtar.