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.
Video game controversies
On 20 April 1999, 18-year-old Eric Harris and 17-year-old Dylan Klebold killed 12 students, a teacher, and themselves in the Columbine High School massacre. The two were allegedly obsessed with the video game "Doom". Harris also created WADs for the game, and created a large mod named "Tier" which he called his "life's work". Contrary to rumor, however, neither student had made a "Doom" level mimicking the school's layout, and there is no evidence the pair practiced the massacre in "Doom".