Zero-K is a FREE, multi-platform, open source Real Time Strategy game, which aims to be a dynamic, action-packed, hassle-free experience, full of clever strategies and constantly moving combat. Includes an epic scale, realistic projectile and unit physics, terraforming terrain and hundreds of unique and interesting units.

Moses_Drayne says

10/10 - Agree (2) Disagree (1)

This is a RTS for the RTS lover. The community is pushing the limit with hectic gameplay and mind-bending visuals. It is a great example of agile community development becoming more than the sum of its parts.