I got one of the greatest 4x games of all time. Sid Meier's Alpha Centauri Planetary Pack. What a top notch game. I still come back to it every once and awhile.
Almost all of my games on GOG are free games I redeemed. The first game I ever bought on GOG with my own money was Cyberpunk 2077 on Wednesday, June 19th, 2019. Hoping I win the Collectors Edition because it has some really nice collectibles!
My first game on GOG was Witcher 3: Wild Hunt, but the first game I purchased on GOG (as in through their store) was Witcher: Enhanced Edition. Everything else was redeemed for free like Witcher 2, Europa, Warhammer, Gwent etc.
"Treasure Adventure Game" was the first game I got on GOG as it was free to grab...
"Fallout Classic" was probably the first game I payed money for on GOG - can recommend.
The only game I currently have on GOG is Oxenfree. Though I lost my old account because I lost the email, so I don't remember what I originally used it for (so long ago in the mists of time). I remember getting Treasure Adventure Game and some Witcher extras from there, though.
Witcher 3 Wild Hunt
I could have sworn that it was something different, like the Wing Commanders or X-Wing series, but I even checked all my emails and the very first one receipt from GOG was for Witcher 3
Wasn't sure if it was purchased, or if it was free, but it was Alpha Centauri. Really need to return to some turn based strategy games, but I'm too busy with Cyberpunk!