Halo 3 announcement trailer

At E3 2006, the Halo 3 Announcement Trailer was shown. Unlike Halo: Combat Evolved and Halo 2, this trailer is in widescreen, HD (High-definition). Cortana's final line within the trailer seems to reference the first of the Cortana Letters.

Transcript
Fade in from white to ruins at the edge of New Mombasa. A comical warning sign depicting a Grunt crossing swings in the wind. The camera slowly pulls back as a gust of wind kicks up a cloud of sand. A flash of blue light flows toward and past the camera, a partial image of Cortana visible.

Cortana: (distorted) "...I have defied gods and demons..."

Cortana vanishes, and the camera continues to back through ruins. A cloud of smoke rises, along with the storm, distorting the familiar silhouette approaching the camera. Again, a transmission from Cortana flashes by, showing her lips moving realistically. Cortana: (distorted) "...I am your shield. I am your sword..."

The figure, which is clearly the Master Chief, walks through the smoke, an Assault Rifle over his shoulder. He stares off to the right. He readies the gun and looks straight ahead. A transmission flashes by showing Cortana's entire face.

Cortana: "I know you. Your past, your future..." Her face fades away into the Chief. Three Banshees fly toward the camera from behind him. We follow them to see an Assault Carrier in the foreground with a fairly sizable Covenant fleet in the background. 9 Banshees (whose pilots' identities are hidden from us) are escorting a Phantom. The Chief stands at the edge of a cliff. We follow the Covenant ships to see a massive Forerunner building in the valley, the Portal. A hole is in the center, and matched above it, a swirling hole in the clouds with a storm raging. A shockwave sweeps the valley as plates in the structure rise. As soon as the shock wave occurred, the Covenant Assault Carriers start moving out of the huge crater. The cliffs start to break away, and the Chief watches his footing. Energy gathers in the center; we see the reflection in the Chief's visor. It fires; fade to white; cut to black.

Cortana: (voice over) "This is the way the world ends."

The Halo 3 logo is shown, and the trailer ends with:  Finish The Fight 2007 

Trivia
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 * If you listen carefully, when Cortana speaks, a voice similar or identical to the Gravemind is saying the same words. This steadily becomes less and less obvious as the video goes on; by the time she says, "This is the way the world ends," the second voice is completely absent.
 * In the beginning, you can see an Easter egg - a "Grunt crossing" sign. Bungie replies-"The New Mombasa City Council had an incredibly efficient public works department until and even during the tragic and devastating Covenant invasion."
 * The debris in the background are the wreckage of the bridge connecting Old Mombasa and New Mombasa and the wreckage of the space tether.
 * It has been confirmed that the mountain in the background is in fact Mount Kilimanjaro.
 * During Cortana's second speech another face can be seen as she says "I am your sword". That face is later mirroring Cortana's face during her third speech.
 * Also, if you look closely, when the shock wave moves across the crater, you can see a Covenant Assault Carrier get pushed away from the middle of the crater. Secondly, if you pay close enough attention, when the shock wave goes across the land, you see Banshees and a Phantom go back in the direction of MC. However, after the scene when the cliffs fall apart, the Banshees and Phantom are gone for some strange reason.
 * Additionally, if you take a closer look at the Banshees you can see that there is nobody flying them. (On the Bungie.net Halo 3 forum, one post offers the possible explanation that the pilots are Elites with camouflage)
 * The enormous hole in the swirling clouds above the middle of the structure in the crater is, according to Bungie, caused by strong, unseen forces from the structure itself.
 * The gun that Master Chief holds looks like the assault rifle from Halo 1. However, Bungie confirmed that it is not the exact same weapon, and is in fact the MA5C mentioned frequently by Bungie in Halo 3 humpday challenges. It is also observed that the MA5C rifle the Master Chief is holding is empty, and its ammo counter shows "00".
 * Cortana says "I know you. Your past, your future..." this could point to that she is predicting (or Gravemind is talking through her) that they will activate the Ark.
 * It is revealed in Halo 3 that this is an early build of the final scene of the fourth level, The Storm. There are a few notable differences, however. First and foremost, the Arbiter is accompanying the Chief, rather than him being alone. The Covenant fleet over the Portal consists of Cruisers and Assault, the Forerunner Dreadnought is within the artifact, and Longsword fighters and UNSC Frigates fly overhead rather than Covenant Banshees. A short attack by the UNSC is added, but ultimately, the portal is activated. Earlier in the level, two Cortana moments show her saying "I have defied Gods and Demons," and "I am your shield, I am your sword," as in the trailer. The line "I know you, your past, your future," is not said, but "This is the way the world ends," is said as the portal sends out a shock wave.
 * Cortana's final line is recited from the Cortana letters "Your poet Eliot got it wrong, This is the way the world ends." This is a reference to T.S. Eliot's poem "The Waste Land" in which he predicts the decay of mankind following World War I. Or, more likely, its referencing Eliot's The Hollow Men, where the the line "This is the way the world ends" is repeated a few times before the last line of the poem.
 * There was once an obtuse rumor going around that you could see the Prophet of Truth if freeze-framing on one of the Cortana Moments which was, of course, ridiculous at that point in time.
 * It is rumored that a secret message is shown at the end of the Halo 3 announcement trailer although no one has decoded it as it is broken up.
 * The Banshees do not seem to be using their boost capability, and yet go relatively fast.

Links

 * LARGE Windows Media trailer
 * SMALL Windows Media trailer
 * LARGE Quicktime trailer
 * SMALL Quicktime trailer