While a proper Steam Summer Sale has yet to be announced, gamers can get their Warhammer 40k fix from the latest Steam deal. "Warhammer Weekend" features several 40k games, expansions, and DLCs for 75% off. The entire Dawn of War franchise is on sale, as well as Space Marine. If you're into giant dudes in badass armor spouting nonsensical holy rhetoric while murdering space orks, this is the series for you.
Dawn of War 2 features two player online co-op throughout the campaign. The Retribution stand-alone expansion features three player online co-op via "The Last Stand" mode. Space Marine supports four player online co-op in its free "Exterminatus" mode. You can see all the sale prices after the break
Warhammer 40,000: Space Marine $7.49
Warhammer 40,000: Dawn of War II - Complete Pack $14.99 Warhammer 40,000: Dawn of War II: Retribution $7.49 Warhammer 40,000: Dawn of War II $4.99 Warhammer 40,000: Dawn of War II: Chaos Rising $4.99 Warhammer 40,000: Dawn of War - Dark Crusade $4.99 Warhammer 40,000: Dawn of War - Gold Edition $4.99 Warhammer 40,000: Dawn of War - Soulstorm $4.99 Dawn of War II: Retribution - Complete DLC Bundle $7.49 Personally, I just picked up the Dawn of War 2 Complete Pack, which includes the Retribution and Chaos Rising expansions. Because I don't have enough games to play.