TAC-21 Sniper Rifle
References to a new weapon named TAC-21 first appeared on 23rd October 2014. Although sounds for the weapon were found in the code, actual audio files were missing.
Players identified this as a new sniper rifle, confirmed by online searches. By early 2016, data miners found an inspection animation for a long weapon larger than the AWP, but no textures or renders were found. It seems developers decided against adding this sniper rifle, as no new references emerged.
Capture the Flag Mode
In 2014, a file named cp_dust2 was discovered, indicating a potential new game mode. It featured flag zones on Dust2 where teams had to lift and carry flags, with opponents able to reset progress. However, this mode was never released, and a 2018 file update likely indicated Valve was trolling data miners, with no further hints of the mode appearing.
Tomahawk, Adrenaline, Bow
Files in CS:GO mentioned several unusual items: the tomahawk, an adrenaline syringe, and a composite bow. While the Falchion, Bowie knife, and classic knife were added to the game, the M48 Tomahawk was not.
In December 2015, an "adrenaline" icon was found, hinting at its possible impact on gameplay. In May 2016, details about a "composite bow" suggested players could control shot power and attach various grenades. These items were known before the "Danger Zone" mode, leading to confusion about their potential inclusion.
Heist Mode
Hints of a "Heist" mode appeared in 2016 with a model of a character from the "Wildfire" operation carrying a sports bag. Papers resembling currency were visible, and a secret parameter named Heist Mode was found. This mode is unlikely to be implemented separately, as related mechanics are used in "Danger Zone."
SCAR-17 Assault Rifle
The SCAR-17 was a highly anticipated weapon, with its mention appearing from the CS:GO beta in 2011. By 2016, details of the SCAR-17 were known, but it is unlikely to be added. Developers likely considered it as a primary weapon for counter-terrorists, which became the M4A4, and the SCAR-17 remains a remnant of the beta phase.