Remove unwanted Tools menu items, including default ones (e.g. "Web Search") and ones created by other extensions. You can always get them back if you need them.
If you've installed lots of extensions, as I have, your Tools menu may be cluttered up (or you may think it was cluttered to begin with). TMO can clean it up with a minimum of fuss.
This is a "light" extension. It only handles the Tools menu, and it won't re-order the items in it. If you want to do more than just remove a few items, I recommend that you get the bigger-but-more-powerful Menu Editor extension (menueditor.mozdev.org).
(For people searching for this: you might also call it Tools Menu Organizer.)