There is a Chrome extension, Disable All Extension Plus which allows to disable all extensions in Chrome at once, if you’re looking for similar kind of extension for Firefox Multiple Addon Deactivator  (M.A.D) is for you.

Multiple Addon Deactivator

Download, install M.A.D extension and restart Firefox browser. M.A.D icon will be hidden in the toolbar which you need to drag and drop onto the Add-on Bar by clicking options>Toolbar layout and by selecting M.A.D icon.

Firefox Multiple Addon Deactivator

M.A.D allows to deactivate one, many or all add-ons at the same time, similarly this add-on allows to activate all add-on at the same time. Double click on M.A.D icon on the Add-on Bar, its user interface displays number of add-ons activated, deactivated and total number of add-ons installed for Firefox.

Disabling/enabling All add-ons in Firefox at once

Select single or several or all Firefox add-ons, click Deactivate all or De-/activate checked add-ons  button and use “Restart Firefox” button to restart Firefox for changes to take effect.

Similarly to activate all/selected add-ons

Click M.A.D icon from its interface, select single or several or all add-ons click Activate All or De-/Activate checked add-ons button and Restart Firefox browser.

You can exclude M.A.D add-on from deactivation by checking the option provided in its options.

Multiple Addon Deactivator options

Multiple Addon Deactivator works from Firefox 4 version.

Download Multiple Addon Deactivator