The well reviewed XCOM: Enemy Unknown hits a new low today on PC, only $16 at Green Man Gaming after coupon. Steam and most other download sites are priced at the full $49.99 list price. Previous low was $17.50 on December 28th for a few hours.
XCOM Enemy Unknown (PC Download) for $16 (normally $50 – use coupon code GMG20-P4DLK-FKYRS). Cheapest ever by $2.