Re-enter the Half Life Universe and revisit City 17 in the time before Freeman, in this fan made single-player mod. The Resistance is threatened by a decisive Combine assault, and as a wanted Resistance member you will need to fight to escape from the Combine's clutch. At the same time, a mysterious force is working towards ends unknown...
I had more fun playing this than I did playing Half-Life 2. Brilliant atmosphere, voice acting, game design -- heck even a well designed boss fight I never saw coming. This is what Half-Life 2 centric campaigns should aspire to!