Halo 2 E3 demo

Halo 2 E3 Demo eG2m4_XVLDM The Halo 2 E3 Demo was a real-time demonstration of early plans for Halo 2's Outskirts and Metropolis levels.

It was shown at E3 2003, and showed some designs for Halo 2, including ODST's, Battle Rifles, (which were originally going to be single-shot), Dual-Wielding, SMG's, Brutes, and many other things.

Differences with the final game
The demo had a vastly different storyline from the final game. Much of it was essentially rewritten to change the events.
 * The New Mombasa Orbital Elevator is nowhere to be seen. Instead, a massive building complex dominates New Mombasa's skies.
 * The Pelican Master Chief lands in is not destroyed, instead it lands normally and disperses its troops without a problem.
 * Master Chief passes through a battlefield hospital before engaging Covenant ground troops in combat.
 * Sergeant Banks is an injured marine who gives Master Chief his SMG, introducing the Dual Wielding feature. He is directing an attack against a Covenant artillery cannon, instead of a Scarab.
 * Brutes attack Earth side by side with the Elites.
 * The Chief is trying to destroy one of many landed CCS-class Covenant battlecruisers, instead of a single Assault Carrier.
 * The Battle Rifle reloads like an Assault Rifle.
 * In the Pelican there aren't normal Marines, there are ODST's inside it.
 * The Master Chief fires the SMG's at the same time, and he never reloads them.
 * When the Master Chief changes to the Battle Rifle from the SMG's, he doesn't drop the other SMG.
 * The battle rifle is semi-auto and has no ammo counter
 * The Shadow's turret shoots green plasma blasts that look like charged plasma pistol shots, not purple shots. Also, it shoots more automatic, it doesn't get faster as it shoots.
 * The Gauss cannon on the warthog fires much faster
 * The Prophet of Regret does not lead the Covenant invasion force on Earth, as he is not mentioned nor is he aboard the Covenant ship above New Mombasa.
 * It is Cortana, not Lord Hood, who outlines the mission (defeat Covenant ground forces and destroy their cruiser, instead of infiltrating their carrier to capture the Prophet of Regret).
 * Only one Pelican, instead of three, heads to New Mombasa. Also the In Amber Clad is not seen.
 * Major Easley does not appear in the final game.

Other Links
It can be viewed here: http://files.mythica.org/halo/halo2_e3_realtimedemo_hires.mov Or downloaded here: http://www.bungie.net/Games/Halo2/page.aspx?section=AudioVideo&subsection=GameVideos&page=1