A dead simple 2D game engine for Go
Game engine supporting many 3D/2D formats and graphic effects
RenderDoc is a stand-alone graphics debugging tool
A homebrew video suite for game consoles
3D-Accelerated open-source DOOM engine
Multi-platform game engine similar to old Megaman with a stage editor
Paintown is a 2d fighting game engine.
Moddable 2D Fighter for Sega Dreamcast
3D Engine technology with partial tools developing kit.