Spring. Or more specifically, the Balanced Annihilation and Extreme Annihilation Total Annihilation mods for Spring.
You're basically playing different versions of TA, but with new units and ways to play... in 3D! This thing fucking rocks. The multiplayer client is cool too.
Did I mention it's free?
The Spring Project
Btw Standardman... nice pick on Zeno Clash! Weird game, but pretty cool nonetheless.