WarDraft II
WarDraft II is an editor for the data archives of the game WarCraft II. The data archives contain a great amount of different files: game graphics, sounds, terrain data, unit properties etc etc. The plan is to give the editor the capability of not only opening and editing the data archives themselves, but also have built in support for editing the files inside.
The project is very far from finished, but it does have the ability to open the archives, decompress the data inside and extract files. There is also support for editing a few of the file types inside. The code is written in C++, and the GUI library used is gtkmm.
Screenshots of the program: