TrenchBroom is a modern, cross platform level editor for Quake-engine based
games.  It currently supports Quake, Quake 2, and Hexen 2, is easy to use,
and provides many simple and advanced tools to make complex and interesting
levels with ease.  Some of its features:

  - True 3D editing, no 2D views required
  - High performance renderer with support for huge maps
  - Vertex editing with edge and face splitting that will not create
    invalid brushes
  - Manipulation of multiple vertices at once (great for trisoup editing)
  - Move, rotate, and flip brushes and entities
  - Precise texture lock for all operations
  - Smart entity property editors
  - Graphical entity browser with drag and drop support
  - Comprehensive texture application and manipulation tools
  - Search and filter functions
  - Unlimited undo and redo
  - Point file support
  - Support for FGD and DEF entity definition files, mods, and multiple
    WAD files