Doom (1993 video game)
The ability for others to create custom levels and otherwise modify the game using WAD files turned out to be a popular aspect of "Doom". Gaining the first large mod-making community, "Doom" affected the culture surrounding first-person shooters, and also the industry. Several future professional game designers started their careers making "Doom" WADs as a hobby, among them Tim Willits, who later became the lead designer at id Software.
Doom (2016 video game)
"Doom"s multiplayer was developed in conjunction with Certain Affinity. SnapMap was developed in conjunction with Escalation Studios and designed to be powerful, to give players the opportunity to create their own content as part of the "Doom" and id legacies, and target those who have no experience or expertise in traditional modding.