I was thoroughly impressed with Eugen Systems' Wargame: AirLand Battle; an extremely complex, realistic take on modern warfare. It's one of the most impressive RTS titles to come out in the last couple of years, and one that was full of content, with a dizzying array of units and factions.
Yesterday, it was enhanced by a completely free chunk of DLC -- a surprisingly hefty chunk. "Vox Populi" has been designed in response to community feedback, adding a new multiplayer mode, a new campaign mode, five new maps, and 24 extra units.
The multiplayer mode, Conquest, is a throwback to AirLand Battle's predecessor, European Escalation's mode of the same name, where victory was dependent not on the decimation of enemy forces, but on the capture of territory. The second additional mode allows players to play through the campaign cooperatively, not just in solo or versus modes.