Favourite computer editing software

You can't get far writing software or documentation without a variety of editors. Here are the ones I use.

Notepad++
A general editor for plain text files, which are required when coding programs. Notepad++ understands a wide variety of programming languages (but not S390 Assembler!), and highlights program artefacts in colour.
Blue Griffon
A flexible HTML editor. It switches easily between Source view and WYSIWYG. In WYSIWYG mode, it uses the same rendering engine as Firefox, so you can be reasonably sure that what you have written will display correctly when it is published.
Inkscape
The de facto standard editor for SVG files. SVG (Scalable Vector Graphics) is a markup language for producing graphics files, that can be used to draw geometric diagrams easily. The SVG markup language is a variant of XML, so it is text-based and can be tweaked with a plain-text editor. The SVG format does not contain any binary data.
SVG cleaner
Unfortunately, the SVG output by Inkscape is horribly verbose. (It can output pixel values accurate to five decimal places, which is nonsense, and just bulks out the markup file.) SVG cleaner tidies all this up and reduces the size of the markup file.
WinMerge
A text file comparison and merging tool. Compares two different versions of a file and helps you to merge the differences.
Hexedit
A hexadecimal editor that lets you inspect and change binary data.
Python(x,y)
A Python distribution that is focussed on producing graphs through its plugin package matplotlib. To be honest, although I have it installed, it seems fairly difficult to use, so I don't feel I have exploited it properly yet. (Beware of linking to pythonxy.com, which now appears to be a recruitment consultancy. Possible domain hijacking?)
Libre Office
This is an open source office suite that is functionally equivalent to the Microsoft® Office® suite, but is free! It is a fork of the earlier OpenOffice.org® suite, but that fell out of favour when it was acquired by Oracle. Open Office was later taken over by Apache, but Libre Office is still preferred by open source purists.
GenoPro
An editor for genealogy data. It allows you to edit relationship links between your ancestors and output the result as an SVG graphic file, or as an hierarchically hyperlinked set of HTML pages.
GIMP
A fully functional open source photo-editing suite that is practically equivalent to Photoshop®, but is free.
MathJax
Not actually an editor, but a JavaScript library that can be used for generating mathematical expressions within a web page.