Nuclear Dawn is an FPS/RTS multiplayer game built on the Source engine, compatible with both PC and Mac. It looks to be a fun shooter, with big maps and vehicles, but one person on each side is in RTS mode and they build a base, research upgrades, give directions etc, just normal RTS things. But considering it's built on Source, the shooter side of it should be a lot of fun. I'm looking forward to it, is anyone else?
http://store.steampowered.com/app/17710/
http://store.steampowered.com/app/17710/