Physion is a 2D Physics simulation software. You can use it to easily create various physical objects (polygons, gears, ropes, springs, pulleys etc) and experiment with their properties. It can be used for both educational and … fun purposes!
Free game editor for your Mac
A free and easy to use game skeleton to be used with Albow
A game level editor
Free and open source Sokoban-like game
Use Sketchup to create levels for the Marathon and Aleph One game engines
apoplexy is a level editor for Prince of Persia 1.
openmedit – Free and open source map editor for the openshooter fps game