If there's one memorable game that you should play it is this one. I just bought it on GOG.com (just released and DRM free).
The amazing thing is that there is an active community modding the game so it runs the best with today's hardware, and it fixes a lot of bugs, adds a lot of unfinished missions that didn't get to the final game, and lots of stuff.
Go check Planescape: Torment out!
And if you get the game, this is an amazing guide to installing all the mods.