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 WAD
"Doom" WAD is the default format of package files for the video game "Doom" and its sequel "Doom II: Hell on Earth", that contain sprites, levels, and game data. WAD stands for "Where's All the Data?". Immediately after its release in 1993, "Doom" attracted a sizeable following of players who created their own mods for WAD files—packages containing levels, graphics, and other game data—and played a vital part in spawning the mod-making culture which is now commonplace for first-person shooter games. Thousands of WADs have been created for "Doom", ranging from single custom levels to full original games; most of these can be freely downloaded over the Internet. Several WADs have also been released commercially, and for some people the WAD-making hobby became a gateway to a professional career as a level designer.