Anton Girdeux wielded a flame thrower which he used to incinerate Rhoemer's Costa Rican Plantation before Gabe and Lian arrived. The Frenchman later brandished this weapon against Gabriel Logan only to be immolated from the inside out when the latter shot a fuel tube connecting the flamethrower to the backpack.
Syphon Filter 2
Gabe Logan himself used a flame thrower against a large group of Spookies while Jason Chance covered him.
Syphon Filter 3
Girdeux once again used this weapon during a flashback, but he himself was not seen in the mission.
Syphon Filter: The Omega Strain
The flame thrower was seen during the IPCA skirmish with CDP personnel, when Russian soldiers used it against American forces. A similar weapon was used by heavily armoured guards who destroyed the Minsk University.
Syphon Filter: Dark Mirror
Red Jack and an unnamed soldier of Red Section used a flame thrower against Logan. The former two were eventually incinerated the same Girdeux was.
In Girdeux's final battle, he used his Flame-Thrower against Logan.
Gabriel Logan and Chance face off against Spookies with a Flame-Thrower.