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.
Tim Willits
Willits has stated in numerous interviews that he was inspired to make video games when he downloaded a shareware version of "Doom". He played the first room of Level 1, thinking that was the entire demo, then, discovering a door that led the player to the other rooms. It was that moment when the door opened, Willits was transported into making video games. Willits required assistance with developing doors in future levels and games. He joined id Software in 1995 after impressing the owners and development team with Doom levels he forged in his spare time and distributed free over the Internet. Willits has worked on "Strife", "The Ultimate Doom", "Quake", "Quake II", "Quake III Arena", "" and "Doom 3".