CnC Red Alert 2
Here's a modification for Yuri's Revenge that adds a whole ton of new units and structures. Each country gets another special unit. Each side also gets spies and if you manage to "borrow"
technology from all three sides of the game, you acquire the ability to build a super base defense: Giant Tesla coil for Soviets, Temporal Incursion Field Generator device for the Allies, and a Psychic Amplifier for Yuri. Needless to say, these defenses are WELL worth the 20,000 needed to construct them.