joy of text
Editor with scripting language, security features & system interfaces.
...It's sophisticated search features can, for example, be used for interactive data mining or automating the extraction of numerical and textual data and reports from arrays of large text files.
It's adaptable user interface, can be programmed to emulate emacs , vi UIs or mouse-driven systems - but who would want to do a thing like that? The display is highly configurable supporting popups, menus-event mouse callbacks etc.
The jot language is terse, powerful and well supported, having a useful debugger and many diagnostic features. Importantly, no mode change is required to enter commands in it's native language.