From Halopedia, the Halo wiki
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, simply referred to as Halo. 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 gameplay 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.
- Bunker - A concrete fortification that may have provided cover.
- Heavy Trooper - Infantry units and an early iteration of the SPARTAN-IIs.
- Scoutcar A.K.A Hummer - An early version of the Warthog featuring a pair of roof-mounted machine guns.
- Zedsu - A conventional-looking main battle tank.
- Stalker - A heavier, camouflaged tank.
- Alien Tank A.K.A Horseshoe crab tank - A large, brown tank. Its design may have inspired the later Seraph.
- Forerunner Tank - An asymmetrical armored vehicle
- Mowitser - Assumably a mortar/howitzer hybrid artillery unit.
- Aliens - The precursors to the Covenant in the final game.
- Starfighter - An aerial vehicle.
- Ghost - Early iteration of the Ghost RAV.
- Other unidentified vehicles - Vehicles similar in appearance to Halo Wars vehicles, such as the Wolverine, Rhino and the cut Cougar.
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 CQL - A 42-round assault rifle with an integral (assumably caseless) grenade launcher. It was named in reference to the MA-75 Assault Rifle/Grenade Launcher in the Marathon series.
- 0x877A 18F8 - An early Okarda'phaa-pattern plasma rifle. It was named in reference to the Alien Weapon "0xfded" error.
- 8W899C-82 - An SRS-style rifle with a chrome barrel and large muzzle brake.
- 12.7mm MP-99 para - A side-loading Human submachine gun with a pronounced muzzle flash. Developers referred to it as "a fire hazard".
- WSTE-M90 Shotgun - A predecessor to the contemporary M90 shotgun, named in reference to the WSTE-M5 Combat Shotgun featured in Marathon 2.
- SPNKR M41 88M - An early version of the SPNKR Rocket Launcher. It was named in reference to the SPNKR SSM Launcher weapons in Marathon.
- 50 Magnum Mega Class M4a - An early version of the M6-series of pistols with an 18-round magazine. It was named in reference to the .44 Magnum Mega Class A1.
- ASW Needler - The pre-Xbox Needler fired higher-velocity projectiles with no apparent homing ability. It used the model of the Portable Minigun.
- SPNKR 108 8AM - A single-shot design launcher similar in concept to the G4H-DuSH. It was named in reference to the SPNKR SSM Launcher weapons in Marathon.
- Pattern-2 Composite Sword - The machete, as featured on the difficulty shield.
- TOZT-21 Defoliant Projector - A flamethrower that sported a similar heat shield to the portable minigun. It was named in reference to the TOZT-7 Backpack Napalm Unit in the Marathon series.
- "The Old Shovel" - A bolt-action, bullpup anti-armor rifle that had to be reloaded after each shot.
- Semi-Auto Shotgun
- Portable Minigun - Handheld rotary gun with a heat shield similar to the TOZT-21 Defoliant Projector.
- Spear Gun - A portable harpoon intended for use against underwater enemies
- Gravity Rifle - A Covenant sniper rifle that vaguely resembles the Type-50 particle beam rifle, its spiritual successor.
- Alien Sniper Rifle - A Covenant sniper rifle that resembles an elongated Okarda'phaa-pattern plasma rifle.
- Excavator - A drum-fed, Fuel Rod-based weapon that resembles the Mauler.
- Unidentified Covenant Grenade Launcher
- Gravity Wrench - A charge-operated Covenant heavy weapon.
- Fuel Rod Gun - Resembles the Fuel Rod Cannon found in Halo: Combat Evolved.
- Fuel Rod Cannon - A Covenant Rocket Launcher equivalent resembling the Fuel Rod Cannon from Halo 2.
- 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 a 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 Karo'etba-pattern Ghost.
- Shadow - An early version of the Wuzum-pattern Spectre, that had a Shade Turret on the back instead of a Pek-pattern 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 lacks 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 has 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 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.
- Sharquoi were intended to feature as a Covenant or wildlife unit.
The Covenant Drinol, now known as the Sharquoi
An early version of the Wuzum-pattern 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, Marcus Lehto (@game_fabricator): "Some were asking about all the weapon names in this old #Halo PC build." (Retrieved on May 23, 2021) [archive]
- Twitter, Marcus Lehto (@game_fabricator): "Robt McLees named them all. I'm not certain I got the above list 100% correct since it's pretty hard to read the text in this build." (Retrieved on May 23, 2021) [archive]
- Unseen4's Youtube Channel - Evolution Of HALO (Beta Pre-XBOX) 1999 version & 2000 Demo
- Marcus Lehto's Twitter - My favorite UI screen to exit the game!
- Twitter: I animated the only existing one...
- Marcus Lehto's Twitter - Stealth Tank
- Marcus Lehto's Twitter - Worm Rock