In Reverse Chronological Order:
In Syfy's Wynonna Earp, the main character wields a demon-killing Colt Buntline Special dubbed 'Peacemaker'. 1
In CW's Supernatural, the main characters and assorted characters wield a supernatural-killing Colt Paterson. 2
It would appear that Wynonna Earp's Peacemaker was inspired by Supernatural's Colt. I'm not going to ask "what inspired The Colt" as that'd be opinion based. Instead, let me be more specific: What works, movies, stories, myths, or literature may have inspired these guns specialized to killing supernatural entities?