Green Man Gaming takes 35% off sitewide via coupon code "WINTR-SRVEY-42012". That's the best sitewide percent-off coupon we've seen from Green Man Gaming. (We saw a similar 35% off coupon a week ago; that was for future purchases and required the purchase of another game before you'd receive the coupon.) Deal ends December 14.
A best bet is Chivalry: Medieval Warfare (pictured) for $12.49 before the coupon above, $8.12 after. That's the lowest price we could find by $17.