So far I've picked up:
Age of Empires II HD + Exp - $7.50 - I'm concerned I may regret this one as it was my least favorite of the real AOE games, back in the day. (I don't consider AOE: Online a real AOE game)
You Don't Know Jack Classic Pack - $5 - I've always loved these games but my original CD for volume one broke in half a few years ago. This pack includes a bunch I've never had.
Pinball FX2 Star Wars: Balance of the Force Pack - $2.50 - Not a big Star Wars fan but I like pinball and figured I may as well pick up this pack since it's 75% off already.
I'm thinking of picking up DuckTales Remastered when Amazon has it for $5.99 in a couple days, which is the same price as the Steam flash sale. Amazon also throws in a promo credit which might be useful.
Sadly, the one thing I really wanted to be on sale is not. I was hoping the Pinball Arcade season passes would be on sale but they're not. The company (FarSight) is actually doing a good job of pissing off their fans by trying to rewrite history in an attempt to explain their recent price increase.