Overwatch is a Half-Life 2 Modification. It's based around a small player base where players play either as Overwatch or the Resistance.
Before I go into detail, start thinking of Zombie Master before you take first thoughts on this. It starts as all the players at the beginning, where they will choose to either 1. Opt for Overwatch or 2. Join the Resistance.
The Resistance are all players, they must work together and use teamwork to complete their objectives and win the round. They can also collect Riot Shields or Medic Kits.
By playing as Overwatch you take control of Dispatch, spanning the map using a birds-eye viewpoint. You control the Combine, (Civil Protection, Overwatch Transhuman Arm, and the Manhacks etc.) You must spawn your units and set them to attack the rebels, it's basically ZM, with a HL2 theme to it.
The reason this never got any spotlights is because it's not in the Official Mod list. I believe this game deserves more attention as it has excellent quality, I will put some links at the bottom to show you what it's like.
http://www.moddb.com/mods/overwatch/images/overwatch-1353#imagebox
http://community.overwatchmod.com/index.php?app=portal
Oh, and don't worry when you see the texture-less areas. The Mod is still in development.