Before Xbox, and before the release of Halo: Combat Evolved, there was a game that was originally announced for the Mac and the PC as a 3rd-person shooter. The game development time was from around 1998 to the release of Halo: Combat Evolved, originating as a Myth-style strategy game before turning into a third person shooter, and finally being retooled as a straight-up FPS for the Xbox console. As the game evolved, several vehicles and weapons were cut and others had complete overhauls. Below are some examples of lost or heavily modified game play items.
Originally, Halo was going to be made an RTS for the Mac. Bungie employees had considered this version of Halo to be a clone of Myth with a Sci-Fi skin over it. At some point, the entire game was redesigned, but was still an RTS.
- Heavy Trooper - Infantry units and early iteration of the SPARTAN-IIs.
- Toolbar - Used to select, command, etc.
- Groundblast - (unknown, possibly a precursor to the leader powers.)
- Zedsu - A tank.
- Stalker - A camouflaged tank.
- Bunker - A structure.
- Scoutcar A.K.A Hummer - An early version of the Warthog.
- Alien Tank A.K.A Horseshoe crab tank - A Tank. Its design was possibly later used as inspiration for the Seraph.
- Mowitser - Probable howitzer cannon due to the name.
- Aliens - The precursors to the Covenant in the final game.
- Starfighter - An aerial vehicle.
- Propane or Gas Tanks - Scenery.
- Ghost - Early iteration of the Ghost RAV.
- Unidentified APC
- Other unidentified vehicles - Vehicles similar in appearance to Halo Wars vehicles, such as the Wolverine, Rhino and the cut Cougar.
- Elephant Precursor - The precursor to the Elephant.
- Sharquoi - Possibly as a Covenant or wildlife unit.
At some point during development, Halo was to be a continuous RPG.
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3rd Person Action Game Stage
Eventually, Halo became a 3rd person action game. These builds of the game are much more similar to the final product than previous builds. Very early versions of the 3rd person version of Halo used many assets from the RTS version.
- MA-5 ICW/30mm COL - An assault rifle with a grenade launcher attachment
- TOZT-21 Defoliant Projector - A flamethrower
- 60 Magnum Mega Class M4a - An early version of the M6 Series pistol
- An SMG - A Human Sub-Machine Gun
- A Sniper Rifle - A Human Sniper Rifle
- A Shotgun - An early version of the shotgun
- Unnamed Gatling Gun - Essentially a hand-held version of the M41 LAAG
- A Spear Gun - A harpoon gun that would've been used against underwater enemies
- Anti-Aircraft Missile Launcher - It's design and concept is similar to that of the G4H-DuSH.
- Anti-Armor Rocket Launcher - An early version of the SPNKR Rocket Launcher.
- Pattern-2 Composite Sword - A machete.
- Covenant Sniper - A Covenant Sniper rifle that vaguely resembles the Beam Rifle, its spiritual successor.
- Another Covenant Sniper - A Covenant Sniper rifle that resembles the Plasma Rifle.
- Excavator - A weapon that resembles the Mauler, but functions like a grenade launcher.
- Unidentified Covenant Grenade Launcher
- Gravity Wrench - A Covenant Weapon that required a charge-up.
- Gravity Rifle - A Covenant Rifle
- Fuel Rod Cannon - A Covenant Rocket Launcher resembling the Fuel Rod Cannon from Halo 2.
- Another Fuel Rod Cannon - This one resembles the Fuel Rod Cannon found in Halo: Combat Evolved.
- Needler - The Needler
- Plasma Rifle - The Plasma Rifle
- Energy Sword - The Energy Sword
- Warthog - Early versions of the Warthog
- Rocket Warthog - A warthog that fires anti-armor missiles (resembles the Gauss Hog)
- Scorpion - An early Scorpion Tank that has a missile launcher on the side instead of machine gun turret.
- Stealth Tank - A tank with a low profile and counter vented fire stabilization.
- Heavy APC - A heavy APC similar to the Elephant.
- Helicopter - A Helicopter that was present in very early builds.
- Pelican - The standard Pelican.
- Boat - A boat that was referred to as the "Dual Carrot Craft" by Bungie Employees.
- Ghost -The Type-32 Ghost.
- Shadow - An early version of the Spectre, that had a Shade Turret on the back instead of a Plasma Cannon
- Wraith - The Wraith Mortar Tank
- Banshee - Early versions of the Banshee
- Covenant Bomber - A cut Covenant Bomber
- In the early versions of Halo, the secondary weapon the player obtained would be placed on their back, though this feature was not present in the final release of Halo: Combat Evolved and Halo 2. This concept was finally introduced officially in Halo 3.
- At some point during development, Blind Wolves were intended to be rideable.
- It would seem that at some point the development team intended underwater enemies to be present in the game, as a harpoon gun existed in these early builds of the game
- In the Evolution of Halo Part 1, there is a Warthog and an ATV that both lack mounted armaments for defense. Both were later planned to be introduced to Halo 2 but dropped and finally added into Halo 3.
- Though the Gatling Gun is not in Halo: Combat Evolved, there have been several mods, using Halo Custom Edition, that have integrated the Gatling Gun into the game. Most if not all of these mods use the Warthog's turret model, separated from the base and the main vehicle.
- Engineers were originally going to be introduced in this game but, like most of this material, was ultimately absent from the final product.
- Though closer to the final product, the E3 2000 build is actually still a pre-Xbox Halo build 
- The Marathon logo was incorporated into the old Heads Up Display.
- An exit game screen existed that asked the player whether or not they wanted to "Retreat from Chucky's Love".
- In the early stages of the game, the Halo Ring was designed to be in broken or incomplete in appearance, only attached by strands of skeletal supports in some areas, not unlike Installation 08's appearance in Halo 3
- The Elites originally lacked the style of armor present in the actual games, with some form of Exo-Skeleton or Tech-Suit instead. They also possessed mandibles that are "more dinosaur-like", rather than having a four-pronged jaw.
- The word "husk" would randomly appear on screen when looking at a vehicle or entity.
The Covenant Drinol, now known as the Sharquoi
An early version of the Spectre, then called the Shadow.
A cut Covenant Bomber as viewed from the front
- Youtube: Bungie PAX Panel 2009
- Bungie ViDoc: O Brave New World
- Twitter: I animated the only existing one...
- Unseen4's Youtube Channel - Evolution Of HALO (Beta Pre-XBOX) 1999 version & 2000 Demo
- Marcus Letho's Twitter - My favorite UI screen to exit the game!
- Marcus Letho's Twitter - Stealth Tank
- Marcus Letho's Twitter - Worm Rock