GOG St. Patrick's Day Sale
GOG.com is currently having a leprechaun-themed sale for Saint Patrick's Day. The sale lasts for a week, ending on Monday the 19th of March. From their announcement:
Come join the festivities - we’re launching with 300+ deals up to -90%, and Leprechaun Hats full of great Mystery Games!
These "Leprechaun Hats" are mystery games that you can choose to buy for $3. After you buy a "hat" you can redeem it to collect a random game from the sale with a sale price anywhere from $3.45 to $19.94 (you can't choose what game you get, but at least you're guaranteed to get something worth more than you paid).
As far as I can tell the only games currently at 90% off are We are the Dwarves and Serious Sam: The First Encounter. At a glance, most games seem to be 66%-75% off.