If you've got an active Amazon Prime subscription and are a Dungeons & Dragons fan, you can now claim the GOG version of Neverwinter Nights: Enhanced Edition for free
Just mind it activates another package, and not the one you'd normally activate when buying straight from the store. And given that, unlike Steam, GOG has issues with packages marking redundant contents as owned, the package in the store won't appear as owned while GOG doesn't manage to fix the legacy code which allegedly causes the issue.
So, if you're like me you couldn't find this right away. I have the amazon games launcher installed and was looking there. You have to go to gaming.amazon.com and login to find your GOG key. I also had one for Prey that I claimed while I was there.