Raw Fury up to -80%https://www.gog.com/promo/20190515_raw_fury
So this is a bit of an odd one, publisher Raw Fury have managed to get sales on both Steam and GOG on the same day for pretty much the same discounted amounts, so really it's a case of pick which store you prefer
You can find the GOG sale here:
and the steam sale here:
Games with discounts include (but are not limited too)
Let us know what games you pick up and from where in the comments below!
After doing a tiny bit of actual research (my bad!) seems this sale extends beyond just steam and gog and into a ton of other stores