0 A.D. (pronounced "zero ey-dee") is a cross-platform real-time strategy (RTS) game of ancient warfare. It's a historically-based war/economy game that allows players to relive or rewrite the history of ancient civilizations, each depicted at their peak of economic growth and military prowess.
Liquid War 6 is an original multiplayer wargame. You have to control an army formed with thousands of pixels that look like liquid, and try and eat your opponent. This is a total rewrite of the (now quite old) Liquid War 5 version. It's still in beta stage, with many imperfections and no network play but it's playable now.
Harris is a strategy game based around the actions of RAF Bomber Command in the Second World War. In Harris, you take on the role of the Commander-in-Chief of Bomber Command, tasked with launching bombing raids against Nazi Germany. It is your responsibility to take the war to the enemy and destroy their capacity and will to wage war.