Leisure Suit Larry
You play Larry Laffer, some kind of 70s reject who is still trying to make it as a swinger in the age of AIDS.
Ostensibly an "adult" game, it is riddled with the sorts of modern cultural references, dirty jokes and stereotypes that most games avoid because of their fantasy settings.
The theme is eminently whistleable, and somehow if people have ever heard it, they will recognize it years after having last seen the game. This is perhaps because most people played it crouched around waiting to see how much actual dirty stuff there was, and because that little tune played over and over and over again.