The ever interesting Escapist has a piece up examining just why Planescapes\ Torment is such a perennial favorite
among gamers and designers alike. From the article: "The strangest, and one of the least successful RPGs from Black Isle (the company that brought you the Icewind Dale series), Planescape: Torment, which was released in 1999, took a risk by using the alternate Dungeons and Dragons campaign of Planescape, a not-really-fantasy, not-really-futuristic world that's mostly defined as unstable and bizarre. Strange and unruly dimensions intersect at the city of Sigil, where most of the game takes place, and your character, portentously called The Nameless One, wakes up in a mortuary with amnesia, a battered shell of a body that cannot die, and just one friend: a flying, talking skull. And the game gets stranger from there."