If you haven't watched through the credits, you are missing a GIANT plot point.


SPOILER ALERT!

If you haven't played Halo 3, or gotten to the ending yet, do not highlight the next sentence, please.

Master Chief, and Cortana, are not dead. That's for if you are too lazy do finish it again, or you highlighted this sentence and just got the SHIT spoiled out of you.

So yes, if you beat Halo 3, watch it until after the credits are over.
It's quite important.