Notepad++ with the TextFX plugin can do this, provided you wanted to sort by line, and remove the duplicate lines at the same time.
To install the TextFX in the latest release of Notepad++ you need to download it from here: https://sourceforge.net/projects/npp-plugins/files/TextFX
The TextFX plugin used to be included in older versions of Notepad++, or be possible to add from the menu by going to Plugins -> Plugin Manager -> Show Plugin Manager -> Available tab -> TextFX -> Install. In some cases it may also be called TextFX Characters, but this is the same thing.
The check boxes and buttons required will now appear in the menu under: TextFX -> TextFX Tools.
Make sure “sort outputs only unique…” is checked. Next, select a block of text (Ctrl+A to select the entire document). Finally, click “sort lines case sensitive” or “sort lines case insensitive”
