Lambda Wars (formerly Half-Life 2: Wars) brings the struggle between the human resistance and their Combine overlords to a multiplayer real-time strategy setting. The Lambda Wars beta only requires Alien Swarm installed to play, but you must own HL2: Episode 2 on your Steam account. It features 3 multiplayer game modes: Sandbox, Annihilation and Overrun, showcasing the Rebels and Combine playable factions and a full-fledged RTS interface and HUD. There is also a singleplayer tutorial and a handful of singleplayer missions.
Lambda Wars is just one of those great mods which reinvents the wheel and makes a game into another genre altogether. The effort and genius itself that went into this mod is worthy of a good rating alone.
I can't wait to see where the mod goes next in future updates.
Lambda Wars (formerly HL2 Wars) is a great RTS mod for Half-Life 2. It's one of my favorite mods by far. Another good thing to know is that this mod is usually updated frequently, and every small detail makes in each change log makes it better.