Halo E3 2000 trailer

 At E3 2000, an early trailer for Halo: Combat Evolved was shown. It was called the Halo E3 2000 Trailer. It depicted events that don't appear in the final game.

A pair of Elites are depicted on patrol, watching a pair of Banshees fly away, when they suddently get sniped by the Master Chief who has a different and more robotic voice than the final one. He then claims that a landing zone is clear, and a Pelican dropship flies in, putting down Marines (a squad comprised of Sergeant Stacker, Private Wang, and several unranked Marines: Geoff, Segur, McLees, and Laine) and a Warthog. They split into two teams, headed for the same destination. As they travel across Halo, they encounter native wildlife not in the final game, namely a pack of Blind Wolves and a group of Thorn Beasts.

The group with the Warthog (McLees, Segur, and Geoff), get to the target first, spotting six Elites, four Ghosts, a Wraith, and what looks like a Spectre. Segur and Geoff attract their attention, drawing the Wraith into range of McLees' Warthog cannon, but Segur is killed by Needler rounds to the head and back. Stacker's group appears, flanking the Elites and killing all of them. They go in the Forerunner structure while Geoff and McLees guard the door. The three marines proceed into an underground chamber where they are soon ambushed and massacred by more Elites, the only Covenant alien featured in the trailer. One Elite in particular is depicted wielding an energy sword in one hand and a large Energy Shield on his other arm. It is possible that it was shrunken and transferred over to the Jackals in the final game. Wang is killed by the Elite with the sword, and Laine is killed on the ramp back to the door. Stacker is killed urging the remaining marines to fall back. McLees covers the door while Geoff takes a Ghost and flies off. Sigurd fails to kill the Major Elite running to a Ghost to pursue Geoff, and is shot by three Minor Elites. A wounded McLees detonates a grenade to take out the Minors before they can fly off in the Spectre vehicle, destroying all the vehicles there.

The Major Elite and two Banshees pursue Geoff and destroy his Ghost. Geoff is wounded, out of ammo, and about to be killed, when the Master Chief appears with an Energy Sword. The Chief then impales the Elite with the Energy Sword. Geoff is evacuated while the Master Chief tells him that his fight is just beginning.

Bungie also made a comedic advertisment "demonstrating" the Nvidia GeForce 2 GTS graphics card using the E3 engine to make the commercial. Link-

Noticeable Differences from the final version of Halo:CE

 * Sound effects for the weapons differ significantly, as do the visual effects used during their firing. Plasma rifles make longer tracer streaks and noises instead of the short-round plasma blasts.
 * Halo is depicted as having an assortment of native wildlife.
 * The Banshees depicted have tail flaps that act as a rudder for aerial steering.
 * An Elite Major uses the Energy Sword to kill one of the Marines. However, that particular rank never uses the Sword in the final version. An Elite Minor was also seen wielding the Energy Sword. In addition to those changes, the real game never appears to have the code for an Elite to lunge, the Elites always appear to swipe, or melee their opponents.
 * The Assault Rifle used by the Marines appears to have a wood finish on various parts.
 * The Marines are depicted to be much more efficient in combat than the final version of the game would prove. Their armor and color of uniform differs slightly, and their rangefinder eyepiece is red, instead of green.
 * The Elites' design is slightly different in some scenes, where it has a lower jaw instead of the four mandibles. Although some of them have do have mandibles as we see in the games.
 * There is an early version of what appears to be the Spectre. It seemingly was meant to be in the game also, but didn't make the cut until Halo 2 came out. This is probably where the Shade turret came from, as there is one planted on top of the Spectre.
 * Look very carefully at the Sniper Rifle the Master Chief was using in the beginning of the trailer. He was wielding the SRS99D-S2 AM Sniper Rifle, which was used later in Halo 3
 * The Banshees' engines sound like the Halo 2 Phantoms.
 * The Master Chief uses an Energy Sword, which he isn't able to do until Halo 2, he has a robotic voice, and a radio antenna on his shoulder. When he is hit by enemy fire, his shields flicker blue instead of yellow.
 * The Elites don't seem to have any shields like they do in the final version of the game since Marines can easily take them down individually with an apparent lack of effort. Surprisingly at the end of the trailer, 18 Elites get killed compared to 5 Marines.
 * The Elite's Energy Shield was like that of a Jackal's personal shield although larger.
 * The Elites also sound very different, with deep and rasping voices, and bear a noticeable resemblance to the noises made by the Flood in the final version.
 * The Elite's Plasma Rifles seem to have more of a purple color.
 * The Marines' Warthog is armed with some kind of light artillery piece. It may be an early version of the Gauss Cannon, which did not appear in the final cut of Halo. It is capable of knocking out a wraith in two shots, rather than the LAAG in the the shipping version. It also glows purple rather than yellow on the windshield and headlights.
 * The only Covenant in the trailer are Elites, no Grunts, Jackals, or Hunters.
 * The Needler's projectiles don't glow. They are more like an explosive version of the Brute Spiker.
 * The Elites hold the Plasma Rifle in a different way.
 * The inside of the Pelican looks different.
 * Some of the energy blasts seem to be from Covenant Carbines, which did not appear until Halo 2.
 * Furthermore, one must notice that the red Elite speaking says: "Your destruction is the will of the Gods. And we are their instruments." Truth says this in one of the first cutscenes in Halo 3. (First cutscene on "Crow's Nest", only difference is that he says "For your destruction is the will of the Gods! And I? I am their instrument." Instead of "And we are their instruments.")
 * The above quote ("Your destruction is the will of the Gods. And we are their instruments") is also featured in the novel The Fall of Reach as the first transmission ever made by the Covenant to the UNSC at Harvest.
 * The trailer plays a few tracks that are very similar to tracks in Halo 3, particularly Greatest Journey.
 * The Fragmentation Grenades' force which the dying Marine activates to kill the Elite is a lot stronger than the final version one.
 * The Pelican in the trailer does not use the NATO phonetic Alphabet in its registration (ie: E419), instead it it just the number 79.
 * When the dying Marine activates the grenade, it actually detonates the parked vehicles, though in the final version they would just flip around with no damage done.
 * The Surviving Marine says to the Chief at the end of the video, "You're Staying?" he then replies that his battle has just begun. This is never said in the final game, but it is the precursor for Halo 3's "Finish the fight" motto. Which might mean that Bungie never forgot that they made the early Chief say this line and use it as a tribute.
 * The Marines seem to run faster than the final game.
 * The Wraith's damage is a lot stronger on the version in the trailer than it is in the final game.
 * Stacker is killed in this, but in the released game, he is seen later on, and in Halo 2, and Halo 3.
 * The Wraith seems to have some kind of energy shield that sparks up where it is shot.
 * The Elites energy shield was destroyed by gunfire but in the final version Jackal's shields can't be destroyed by gun fire.
 * Marines don't run out of ammo in the final version.

Trivia

 * The Elite Major says that your desctruction is the will of the gods, and we are their instrument, which is excatly what Truth says in Halo 3. It is also a message said by the covenant in Halo the Fall of Reach