SWAT 3: Close Quarters Battle (also known as SWAT3 or SWAT3:CQB) is a tactical squad-based first-person shooter, developed by Sierra Northwest and published by Sierra Entertainment for Windows-based PCs on November 23, 1999. It is the seventh installment of the long-running Police Quest and SWAT series.
This is the M79 Grenade Launcher from the Swat 3 TGOTY CD, It is built in game to fire either CS Gas canisters or Flashbangs. This file isn't by me nor do I take credit for it, This file was uploaded on the Swat 3 Reunited website and it was reuploaded here to get interest in Swat 3 again.
Drag the M79 file to the file directory:Sierra/Swat3/Mods. Enable via the swat 3 mod launcher and bam, There is the mod.