While at Nintendo he developed the hugely successful Game & Watch games and the Game Boy Hand held console. He was also the producer of many hit games such as Donkey Kong, Mario Bros. and Metroid. He was also a producer of Tetris Attack (scored by Masaya Kuzume) and Fire Emblem: Seisen no Keifu (scored by Yuka Tsujiyoko). The low point in his career was the commercial failure of the Virtual Boy.
In 1996, Yokoi left Nintendo to form a new company, Koto. There he developed the Wonderswan, another hand held console. The first game released for the Wonderswan was named "Gunpey" in his honour.
In 1997, Yokoi was tragically killed in a car accident. He was riding a car driven by Etsuo Kisoo, a businessman from Kyoto. Kisoo and Yokoi pulled over to examine the damages to the two automobiles, and then a car driven by Iwao Tsushima of Yamanakamachi, Ishikawa Prefecture, slammed into the two men. Kisoo endured two broken ribs, and Tsushima and his wife were mildly injured. Many of the employees of Nintendo of America closely worked with Gunpei Yokoi.