As a teenager, I wrote a feature-rich Minesweeper clone in Borland Delphi. Unfortunately, I lost the source code, but the binary for Windows is here.
For my research in representation theory of finite groups, I wrote numerous algorithms for the computer algebra system GAP. These can be found on github.
As a way to learn Python, I wrote a Mastermind clone with a graphical interface using PySimpleGUI. In connection with my lectures on combinatorial group theory, I also developed a permutation puzzle based on the word problem. Source codes of both projects can be found on github. Binaries for Windows and Linux are here. The Linux binary requires certain library versions.
Most recently, I programmed a simple tool for interactive rows/columns permutation of matrices in C++ using wxWidgets under code::blocks. Linux binary is here.