My Rating: 9.8 / 10

    The second expansion to Half-Life places you in the shoes of security guard Barney Calhoun, a good friend of Gordon Freeman (though you don't really learn this until Half-Life 2 and beyond). Following the resonance cascade, Barney is forced to fight for survival against thousands of alien enemies while trying to escape from Black Mesa.

    This expansion was developed by Valve, not Gearbox like Opposing Force. This doesn't mean much by itself, but I believe the overall quality of the game was far beyond Opposing Force. A perspective of the Black Mesa incident rivaling Gordon's perspective makes this a must-play for Half-Life fans in addition to the first expansion.