I have always loved using Firebug for my browser specific developer tool because of the fast loading times, the nice button i could just click on to enable it, and the ease of use and navigation. I've recently started to really enjoy using Opera's Dragonfly. I love the color palette that it has as well the awesome zoom feature that Opera has built in. So my question is what is your favorite set of browser specific developer tools and why can't you live without them?