A powerful editor for video games based on or similar to id Software's series of Quake games. Currently QuArK supports 41 distinct games, 5 generic game engines, and a countless number of expansions packs, addons, and mods. It integrates a map editor, model editor, archive editors, texture management, and much more.
The 3D Slicer is freely available, open-source software for visualization, registration, segmentation, and quantification of medical image data. Follow the link for more info: http://slicer.org