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.
Easily the best multi-platform RTS that I have discovered.
when you get past certain members of the community everyones pretty cool