My latest passion is cheating at solitaire.
One of my favorite hobbies is reverse engineering and modding video games, old and new. Zachtronics recently released a bundle of solitaire games collected from all of the wonderful games they released over the last couple years. I built a program that injects code into the game, reads the game's memory to find the board state, and passes that into an automated solver. I also figured out various ways to trick the game into thinking that the board has been solved.
Reverse engineering games is incredibly fun, and you can learn a lot as well!