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.
Chex Quest
The development of "Chex Quest" differed from traditional video game development in that the basic game engine had already been created and the bulk of the creation process consisted of aesthetic changes made to the music and artwork from "The Ultimate Doom". For budgetary reasons, Id Software was contacted and an inexpensive license was obtained for the "Doom" engine which was considered obsolete in light of Id's recently released "Quake". "Chex Quest" was the first foray into professional game development for lead artist Charles Jacobi and programmer Scott Holman, though both had previously modded "Doom" levels in the past. In an interview with PC Gamer magazine in 2009, Jacobi stated that the biggest reason for the lasting success of "Chex Quest" has been that it is still essentially a disguised version of "Doom" with basically unaltered game dynamics. Indeed, the game has been recognized for having a sense of humor about its identity and origins.