GalGen Trader is (or at least will be) a 2D space trading and exploration game set in a complex and persistent procedurally-generated universe. Dwarf Fortress in space, if you will.
One of its most important features is the ability for extension modules to be added that can change just about any feature of the program; from new weapons and devices, to adventure modules that add new 'mini-plots' (similar to the Galactic Adventures DLC for Spore), to modules that replace parts of the core...
All Ahead Flank! (AAF) simulates modern tactical naval combat in real time, including surface, subsurface, and air threats. Multiple factions and players are supported, and the perspective is that of a flag officer in command of a group of assets.