One of the major drawback that I felt while using Firefox was unavailability of double click on the Tab bar.
As it worked in IE, that when you double click on a tab it automatically closes it and double clicking anywhere on the empty space in tab bar opens a new tab.
This feature proves to be very handy while browsing and users can very easily close or open new windows without looking at the tiny ‘x’ that allows us to close the tab.
So here I found a nice tiny add-on for Firefox and Flock that allows us to do the same.
See Tab Clicking Options for use with Firefox.
See superT for use with Flock.
Configuring these addons is very easy, you just have to set your favorite shortcut to do the desired action.
Give it a try !