The Dungeon Keeper games are some of my favorite, though if you run a 64-bit computer, they take some tweaking to get running. The Baldur's Gate and Icewind Dale games are great fun as well, if you like that style. Planescape is supposed to be pretty good, I haven't gotten around to playing it yet, so I can't say. Arcanum: Of Steamworks and Magick Obscura is a pretty fun Baldur's Gate style game.
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I have the best friends ever.
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