Arianus: Divinity 2 Dragon Knight Saga
DrIstvaan: I agree it has a neat story (maybe not as great as that of some others listed here, it's still more of an ARPG after all, but very memorable, especially regarding the characters involved), too bad it's not on GOG, thus doesn't comply with the thread title.
Anyway, I'm playing it through for the second time right now, in quick succession, it's that good as a game :-).
(OK, I'll stop derailing the thread now.)
The only reason I posted it was because the OP offered games that wouldn't be offered on GOG, example Bioshock 1,2, Mass Effect, or Dragon Age.
But yes I agree awesome game and it won't be on GOG for awhile.