Arc

"ARC! Attack - Retrieve - Capture - that's what ARC is about. Join one of four mini-armadas, mixing it up with as many as 64 players at a time in this free, Internet-based, multiplayer action/strategy game. Capture your rivals' flag, dominate the map or crush all opposition. Fast, low-latency and effortless to install, ARC launches you into the team multiplayer experience with a full payload of adrenaline and it's ABSOLUTELY FREE!"

Free to play indefinitely.