Crypt of the NecroDancer is flash-selling right now for $7.50. I wholeheartedly recommend it.
And
Rogue Legacy is flashing for $3! Also recommended!
Also, they were all sneaky; The Witcher franchise is on daily sale, but Witcher 3 is still what is was before. This is why I don't end up with the bigger titles until years after everyone else; I'm not comfortable paying three times the price for a game compared to others I might enjoy just as much.
After watching
this, I'm totally tempted to pick up
Duck Game. I've posed an open invitation to my friends, but in the event they aren't as enthused, I'll probably be looking here.
EDIT2: And if it goes on daily/flash, I'm also now recommending
Massive Chalice. It's pretty fun!