You Cannot Oppose This
Opposing Force is a side story that expands on the Black Mesa incident from the first Half-Life, and takes baby steps into the concept of squad and class based shooters like Republic Commando or Return to Castle Wolfenstein. The game puts the player into the shoes of Commander Sheppard, (long before Mass Effect or Stargate: Atlantis's "Commander Sheppards") a military officer sent in to "sanitize" Black Mesa and cover up all traces of what happened there. It's a solid FPS game and worthy bearer of the Half-Life brand. You'll be on the trail of Gordon Freeman, the scientist who escaped capture and has made it his hobby to kill all your friends. It's clever in the way that you get to see the other side of the a conflict. The game also explores different areas of the Black Mesa facility that weren't seen in the original. The military special forces are your friends this time around. Instead of getting health from the dispensers on the wall, you have to keep your medics alive. Engineers at your command are used to blow up roadblocks or cut through doors. The eventual fate of Sheppard is left in limbo, like Freeman at the end of the first game. I presume they're saving him for Half-Life Episode 3 in some big all-star reunion with Gordon, Barney, Alex, Chell, and maybe the Left 4 Dead survivors. If you enjoyed Half-Life, you'll enjoy Opposing Forces.