Fascination (lost unreleased adult Nintendo arcade game; 1974)
In 1974, Nintendo released Wild Gunman, an arcade game that used 16mm film rather than video. It was a light gun shooter where the player engages in a gunfight with various Old West-style outlaws. The gunmen were represented via film footage of actual live-action people. The player had to watch for the opponent's eyes to flash, then shoot at them. 10 years later in 1984, it inspired the Family Computer/Nintendo Entertainment System game of the same name.
Nintendo also designed a more adult version of the game, known as Fascination (ファッシネーション). It was also a shooter using a light gun, but the film was significantly different. Instead of shooting cowboys, the player shot at a Swedish woman in an evening dress who danced around the screen. When she struck a pose, the player shoots. Instead of killing her, parts of her clothing come off. The process was repeated until she was completely nude.
This game was never released to the public, and likely due to the company wanting to keep a "family-friendly" image, they rarely mention it.
However, Gunpei Yokoi - famed designer at Nintendo - specified that they didn't release Fascination because its mechanism was too "complicated and fragile".
Fascination should not be confused with the 1991 point-and-click adventure game of the same name, which is also erotic-themed and developed by a studio that would then put on a family-friendly image (Coktel Studios).