Mh I saw many people liked these question of me, so I just do another one! I definitely had most fun coding my self learning stock ai and my machine learning drone.
For me, I enjoyed creating things that helped me in school. I made a Punnet Square Probability Engine and a Linear System Equation's solver. I showed these programs off to my friends and their response brought a lot of pride to my coding.
Probably my original website. I've been creating a website that displays the periodic table of elements. The urge to develop this website essentially caused me to start doing web development. That was the beginning of this past summer. I have a huge emotional connection to the project due to the time I've invested in it. The program that I dislike the most was actually a complete rewrite of the aforementioned app. It was much slower despite being architected better - I scratched that and now I'm working on the original.