Use the voucher code CIVIL-IZATI-ONGOD to get Sid Meier’s Civilization V: Gods & Kings for $22.95 (25% off). Requires the base game and it uses Steamworks.
Voucher code DEATH-SAVES-TODAY gets you 25% off Darksiders II Limited Edition, which makes it $38.20. Also uses Steamworks. This is a pre-order. Game has an August 14, 2012 release date.
Both voucher codes expire at 1100 UTC 22nd June.