Easily one of the most unique and interesting universes in any medium, Planescape was the high point of the AD&D system and gave us the much-loved CRPG title Planescape: Torment.
Considering that it constantly ranks among the top listings of RPGs, its bizarre that there's never been any other games placed in the same setting. There was in fact a first person title in the works slated to release on the PS1 that would have put you in the role of a member of the Harmonium, policing the wild streets of Sigil.
Sadly (or not, if FPS games aren't your thing), it was scrapped six months into development. It might not necessarily have been in the spirit of the classic Torment, but its not like going first person is an unprecedented style shift, with games like Dark Messiah Of Might And Magic or Fallout 3 making the leap.
With Wizards Of The Coast not letting anyone else use the Planescape license, its unlikely we'll ever get another video game placed in this long lost multiverse. But then again, considering the quality of recent D&D titles, that may be for the best: just take a look at Daggerdale or Sword Coast Legends.
All is not lost though! InXile is gearing up to release Torment: Tides Of Numenera in Q1 2017. While no longer set in Planescape for legal reasons, all the same bizarre oddity and interesting moral choices are slated to set a very similar tone.