I just recently downloaded and listened to the Black Mesa score from the fan re-visioning of the original Half-Life game using the Half-Life 2 source engine. I really like the takes on the original score and new directions they decided to go. The score is free so no reason not to pick it up.

One song, "Apprehension" is featured above. The score seems to paint pretty awesomely broad strokes for what game scores can be and it inspired me to give Black Mesa a shot.