The Substance Indie Pack is currently £94.99 (Includes Substance Painter, Substance Designer, Bitmap2Material and 30 PBR Substances). (Edit: NanoTurtle already posted but heres a link anyway :P). http://store.steampowered.com/app/287280/
Voted for Substance! Already have it but the more people supporting them the better :)! Annnd may have bought Serious Sam 1 HD for nostalgic reasons. $2 I may never actually use..
I was hoping for a larger sale on Substance Painter rather than SD4 as I don't use it in my workflow but I would love to start using it. On an unrelated note, Mixamo Fuse looks great because of that autorigger. I'm tempted to pick that up if it goes on sale for that feature alone.
I bought myself the Substance Package. I don't think it's really worth waiting for it to have a flash sale cause we don't even know if it's going to have a flash sale, and it doesn't make too much of a difference in the long run. Plus, I was too excited to work with it to wait.