This is the flamethrower featured in the maps 'Trapped' and 'Necropolis'. Included are the models, sounds, materials, scripts, and particle effects for your own custom maps. Please note: you MUST HAVE SOURCEMOD INSTALLED and the Flamethrower.smx plugin to make it functional.
Head on over to the forums if you're having problems. There's a thread posted with installation instructions.
TurdBurglar and Stay Puft