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 (franchise)
The "Doom" video games consist of first-person shooters in which the player controls an unnamed space marine also referred to as "Doomguy". The player has to battle the forces of Hell, consisting of demons and the undead. In the games, the player's character will often go back and forth through hell. "Doom II: Hell on Earth" follows after the events in "Doom", the player once again assumes the role of the unnamed space marine. After returning from Hell, the player finds that Earth has also been invaded by the demons, who have killed billions of people.