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 (1993 video game)
The "Doom" game engine was licensed by id Software to several other companies, who released their own games using the technology, including "Heretic", "", "Strife: Quest for the Sigil", and "Hacx: Twitch 'n Kill". A "Doom"-based game called "Chex Quest" was released in 1996 by Ralston Foods as a promotion to increase cereal sales, and the United States Marine Corps released "Marine Doom".