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.
Official versions of Doom
The first version of "Doom" for Windows was released under the name "Doom 95", on August 20, 1996. It was compatible with Windows 95 and up, and was able to use WADs from the MS-DOS versions. It also allowed users to set up multiplayer games much easier than in DOS. It was included with "Final Doom". The port was project-led by Gabe Newell and other later founders of Valve Corporation.