The Hellfire Gun is a small shotgun that fires bursts of Hellfire. Unlike conventional sidearms, the Hellfire Gun never runs out of ammunition and can be fired repeatedly for an indeterminate amount of time. During the period when Johnny Blaze was separated from the Spirit of Vengeance known as the Ghost Rider, he used the Hellfire Gun to fight off demonic threats.
When the Mother of Demons named Lilith manifested on Earth, the Hellfire Gun proved vital in its ability to destroy Lilith's demonic offspring the Lilin. One of the Lilin called Creed threatened Johnny's family, so Blaze destroyed him with repeated blasts from the weapon. Creed was actually grateful for the assault and told Johnny that he finally brought him a measure of peace.
During the events of Road to Vengeance, Johnny Blaze uses this weapon to calm down Vengeance.