Beta Weapons are weapons that were removed from a Grand Theft Auto game during its development. It also includes some weapons that didn't make it to the final game and weapons have their models changed, and some still exist in the game files. Many made well during development and it is unknown why they were removed. However, most of them can be obtained through cheat device and trainers.
The Skateboard was cut from the PC version. It is primarily a melee weapon but also a vehicle. Available as a mod for the PC version but is not usable on the PS2 version.
The Micro SMG known from GTA VC was also removed, but can be seen in several early screenshots.
The later Mini-Uzi based Micro-SMG was originally more detailed.
The MP5-K was cut. It was most likely replaced by the MP5 or TEC-9. It also lacks a texture.
The M47 Dragon was cut, it was most likely an Advanced RPG (like a Heat Seeking Rocket Launcher) and due to being an Anti-Tank weapon, most likely larges amounts of damage. However, the weapon is mentioned in an Ammunation advertisement.
The Nail Bat was cut, it was most likely a more powerful baseball bat. Even though there are no textures in the files, the Nail Bat however uses the texture mapping from the cut Manhunt Nailbat.
The PSG-1 was cut, strangely the in-game HUD for the Sniper Rifle resembles the PSG-1. Interesting enough a model in the files lacks a textures, which appears in Manhunt. The PSG is most likely mentioned in an Ammunation advertisement as a "High Velocity Rifle".
The Barrett M82 was originally intended to appear, being most likely being the most powerful non-explosive weapon. Oddly, the model is highly detailed compared to most weapons.
The M-60 and the M249 were both slated to appear. However the M249 appears not to have been finished. They were most likely both heavy weapons, possibly even being purchasable from Ammunation.
The M16 was intended to appear, possiblt as an Army exclusive weapon (As the M16 is the US Army's official Assault Rifle). Despite not having a texture in the files, it is mapped to use the M16 textures from Manhunt.
A Pistol resembling the Thompson-Center Contender was intended to appear (It would later appear as the Marksman Pistol in GTA V)
An unused Second Dildo and Vibrator exist, it is possible to spawn these using trainers.
A sniper rifle resembling an SR-25/Mk 12 can be seen wielded by both Michael and Trevor during some artworks, also in the newer update files the cut SR-25/MK-12 Hybrid HUD and texture files could be found. It is named Assault Sniper in-game.
In the trailer, Trevor can be seen holding an assault rifle with a Laser Sight attachment. This was also seen in another screenshot where it is seen in use by a police helicopter sniper.
Some weapons had an older more realistic wood-cast model.
An Beretta 92FS/M9 Pistol was meant to appear but was probably replaced by the ongoing Taurus PT92.
One of the pistols (not confirmed which one) had the same shooting noise as the pistol from GTA IV, as Lamar is seen shooting one out of a car in Franklin's trailer. This may have been a placeholder.
The Rocket Launcher originally had an optional grip attachment, as seen in the official BradyGames Guide. It was taken out in the final game.
The Sawed-Off Shotgun had wooden grips.
Several of the weapons in the Beta much more resembled their real-life counterparts (i.e the Bullpup Shotgun resembled the KSG more clearly, and the Combat MG looked more like the FN Mk 48). This can be seen in the HUD icons for some of the weapons as well as the beta models of weapons such as the Assault SMG and Combat MG.
Some weapons such as the Assault SMG and Combat MG were originally modified from their TBoGT equivilents before being changed, whether to avoid copyright infringement or for creativity reasons.
An artwork for the High Life Update suggests that the Bullpup Rifle was originally modeled after the British L85A2 assault rifle. In the final version, it is based on the Chinese QBZ-95.