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.
Brutal Doom
Brutal Doom is a gameplay mod for the video game "Doom". Developed by the Brazilian modder Marcos Abenante, a.k.a. Sergeant_Mark_IV, it adds numerous features to the gameplay. The mod has been in development since 2010, and continues to release new updates. The most current version is v21b.