Eureka is a map (WAD etc.) editor (based on Yadex) for the classic
DOOM games, and a few related games such as Strife, Harmony, HACX,
Heretic, and Hexen.

It features multiple-level undo and redo, a 3D preview, texture and
thing browsers, a built-in nodes builder, panels for directly editing
the properties of map objects, a flexible key binding system, and low
system requirements (e.g. a 3D card is not required).

WWW: http://eureka-editor.sourceforge.net/