https://www.pcgamer.com/get-ten-percent-off-select-gog-purchases-for-the-next-48-hours/

For the next not-quite-48 hours, GOG is offering a ten percent discount code on certain games including Crossing Souls, The Legend of Heroes: Trails of Cold Steel 2, Hellblade: Senua's Sacrifice, and The Witcher 3 Game of the Year Edition. To score your discount, just click this link and then the "continue" button, at which point you'll be taken to the following list: 

Pick as many you like, and then be on your way. Obviously these aren't the deepest discounts ever, but if you don't feel like waiting for the next big sale to roll around, there you go. The GOG surprise discount dealio will be available until 8 am PT/11 am ET on March 2.