PSPad

PSPad (Windows only) http://www.pspad.com/ :  
Text editor and source editor which is more powerful and useful than notepad and wordpad that are standard with Windows.  PsPad allows for row and column selection of text, macro creation, file comparisons, tabs for multiple documents, language syntax highlighting, regular expression find/replace capabilities,  among other advanced features.  You can either download portable version or install full version to integrate with Windows shell.