Suppressor

The Suppressor, or silencer, is a device attached to the muzzle of a firearm to deafen its firing sound and suppress its muzzle flash; it also limits the recoil of the gun. It is used on some weapons in the GTA series but comes standard on them and cannot be removed. However, in GTA V, the suppressor can be used as an optional attachment for most weapons.

Grand Theft Auto 2
The silencer first appeared in Grand Theft Auto 2 on the Silenced Machine Gun. The silencer's only purpose is to make pedestrians and cops oblivious to to the gunfire.

Grand Theft Auto: Vice City
In Grand Theft Auto: Vice City, the suppressor appears on the PSG1, though it serves no purpose other than aesthetics.

Grand Theft Auto: San Andreas
In Grand Theft Auto: San Andreas the silencer appeared on the Silenced 9mm. It serves the purpose of stealth, as firing the silenced 9mm will not alarm any pedestrians, unless the pistol is pointed directly at them, nor will it attain you a wanted level, unless fired directly near a police officer.

Grand Theft Auto: Vice City Stories
In Grand Theft Auto: Vice City Stories the silencer appears on the Mac 10, though it serves no purpose other than to make pedestrians and cops oblivious to gunfire.

Grand Theft Auto: The Ballad of Gay Tony
The suppressor makes appearance again in Grand Theft Auto: The Ballad of Gay Tony, this time on the Assault SMG. The suppressor serves no purpose other than to suppress the muzzle flash of the weapon.

Grand Theft Auto V & Grand Theft Auto Online
The suppressor is an attachment in Grand Theft Auto V and Grand Theft Auto Online that can be mounted on several weapons:
 * Handguns: Pistol (and its Mk II version), Combat Pistol, AP Pistol, Pistol .50, Heavy Pistol, Vintage Pistol, SNS Pistol Mk II
 * Shotguns: Pump Shotgun (and its Mk II version), Assault Shotgun, Bullpup Shotgun, Heavy Shotgun
 * Submachine guns: Micro SMG, SMG (and its Mk II version), Assault SMG, Machine Pistol
 * Additionally, the Combat PDW features an integral suppresssor
 * Assault: Assault Rifle (and its Mk II version), Carbine Rifle (and its Mk II version) , Advanced Rifle, Special Carbine (and its Mk II version) , Bullpup Rifle (and its Mk II version)
 * Sniper: Sniper Rifle, Marksman Rifle (and its Mk II version), Heavy Sniper Mk II

When equipped, the attachment dampens the firing sound and suppresses the muzzle flash of the weapon, making it able to perform stealth kills, unless there are witnesses that will alarm the police. The protagonists will not shout taunts whilst firing suppressed weapons (eg. "You want me, huh?", "So kill me!", "Screw you!", ect).