Firebug - Best firefox plugin?

If your even the tinyest bit into web development, and you havent heard about firebug, you deserve a slap. Literally this is one of THE best plugins available for firefox. It is so handy when 

trying to fine tune those pixel perfect widths and alignments. Not only can you control elements from within the browser to test exactly how it will look if you tweak something, but also you can disable stylesheet attributes directly on the page too. Not only this, but one of the most handy features, is the abilty to 'inspect' and element, and then simply check the layout button, and read off all of the attributes, for example left position. This makes it perfect for fixing layout imperfections, and graphics that don't quite line up properly.

All in all, definately one of the best plugins available for firefox, and if you do any form of web development, and dont already use it, shame on you!