SciTE is a developers editor. Originally made as an example for the Scintilla project - an open source source code editing component, SciTE today is a fully featured text editor for developers using virtually any programming language.
Apart for the standard syntax highlighting and code folding features - SciTE also understands error messages from compilers/interpreters allowing it to quickly pinpoint where in the source file the error occurred.
The functionality of SciTE can be extending using scripting. And it can even be "remote controlled" using scripts on Windows.