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.
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.