To open the Firefox developer tools, press Ctrl-Shift-K. This is good if you have Firebug installed, as F12 will open it instead.
To take a full-page screenshot of a web site, press Shift-F2 and then type this command and hit press ENTER.
This will be saved in the ~/Downloads folder by default.
There is more information about the Firefox command line here: https://developer.mozilla.org/en-US/docs/Tools/GCLI.
The wrench icon on the command line bar will open the developer tools. This is a useful shortcut to leave open on the bottom of your Mozilla Firefox window.
Press Alt-D to select all text in the URL bar if you wish to copy the text to the clipboard.
In Firefox, hitting apostrophe ( ‘ ) allows you to type and only search for links.
Control+Shift+T. Reopens your most recently closed tab.
Shift + F10 to simulate a mouse right click from the keyboard. If you have to interact with Windows without a mouse this one is a life saver.
The Ctrl-Shift-P shortcut In Firefox switches to incognito mode.
Use Ctrl-Tab to cycle through open tabs.
Ctrl-Shift-J Open the Browser Console to troubleshoot an unresponsive script error.