My first game, written in Game Maker in 2016: a user in /r/gamedesign proposed a challenge to create a game in a week, on the prompt "changing seasons." I hadn't completed a project yet, and decided that the mad dash to start and finish a whole game in a week would be fun. It was!
The game is of course fairly buggy, but I'm proud of finishing my first-ever game with all of my own code and art and music assets.