FXiTe is a portable editor for plain text files. It's targeted at developers, but is easy enough for anyone to use.
Open an existing text file, say, and you can edit it just as though you were using Notepad. There are no extra complications, nothing else to get in your way (although the slightly odd toolbar, with coloured text buttons instead of icons, is a little distracting at first).
It doesn't take long to notice FXiTe's advantages, though. Like the tabbed interface, which makes it easy to open multiple files and switch between them. Indentation support. A Zoom option, for faster browsing of long documents. Drag and drop editing (select some text, drag and drop it somewhere else). The ability to insert one file within another. Powerful search and replace tools with regular expression support. And the option to export documents in PDF when you're done.
Software developers get even more, with built-in syntax highlighting for 40+ languages, macro recording and playback, easy integration of external tools, a message window to display the output of those tools (compiler error messages and so on), even an embedded Lua scripting engine.
A quick check of the Settings dialog reveals plenty of other interesting options. You can define the look of the program, tweak the toolbar, customise hotkeys, set your preferred text font, and modify editing behaviour. There are useful extra features, too, like the ability to back up your current files on a regular basis (Edit > Preferences > General > "Backup files every x seconds").
What you won't get is an integrated Print option, oddly. And FXiTe doesn't have the raw power of some Notepad replacements, either (you can't sort lines, case manipulation options are relatively limited, there's no support for multiple clipboards, you can't run a search and replace across multiple files, and so on). It remains a likeable editor, though, and features like built-in PDF export and its extreme configurability mean FXiTe will serve most people very well.