Penumbra: Black Plague
Black Plague focusses on the best parts of the original game (the creepy atmosphere and physics based puzzles) while trimming the worst parts (the combat) making it a better experience overall. Playing the original is still required to make the most out of it and it is a little on the short side but it made me jump quite a few times which is commendable.
Gameplay: Removing combat ramps up the atmosphere considerably.
Graphics: Better looking and featuring more detail than the original.
Sound: Solid voice acting and lots of creepy ambience