Command & Conquer

Command & Conquer was developed by Westwood Studios, and released in 1995 to very positive reviews. It is credited with defining the real-time-strategy genre (although much of its gameplay was based on the company's earlier game Dune 2). Combining a detailed playing field, fast responsive gameplay and a story told through video cutscenes, the game has influenced almost everything that has followed in the genre and spawned numerous sequels of its own.

Placed in the middle of a war in the near future, you can choose to command one of two sides: GDI (Global Defense Initiative) or the Brotherhood of Nod. Controlling various units, you have to wage war on the opposing side while maintaining your base and resources. The game consists of 15 objective-specific missions for each side.

freeware
as of 2010 Command & Conquer(along with the add-ons/DLC) had been change to freeware.