Not an absolutely necessary extension, but one that saves a lot of time from having to search through menus Rated 5 out of 5 stars
Hides unneeded and unwanted menu items and allows the user to organize the rest. Result: BAM! Makes it easier and faster to find what you're looking for. Only quibble with it is that developers have seemed to have abandoned it before implementing customization of the bookmark and history menus, as well as the app bar (which may have been added to Firefox after ME was released) menu. UI Eraser will help those who want to remove items from menus, but doesn't help with sorting or organizing UI elements.