4. Grand Theft Auto: San Andreas's Infamous Hot Coffee
Which is very fan fiction-y, but is nothing compared to the decadent heights of Grand Theft Auto. You've been able to pick up sex workers in your car and regain your health in most instalments of the franchise, but it was San Andreas that introduced the concept of dating and if you played your cards right, your character might be invited in for coffee after. Surprisingly for the GTA series, there was then a tasteful fade to black as CJ and his mistress of choice knocked boots, but originally developers Rockstar had considered a very different approach. Eventually uncovered by some judicious hacking and poking around in the game's source code, there was a whole sex-having mini-game. Nicknamed Hot Coffee, the low-res Playstation 2 models look utterly terrifying as you manipulate them around each other with the grace (and control scheme) of a Dance Dance Revolution. Who knows why Rockstar eventually abandoned this whole other set of levels and mechanics, but they've never gone back to it with later titles, either...