Doloto - useful addition to a Web Developer's Toolkit

I have been using the following Web Development tools over the past few years and they have helped me to be more productive -

• Firebug
• YSlow
• neXpert
• Fiddler

I discovered 2 new tools that not just tell you what is inhibiting performance of a page but also cut the fat off web pages making them speedier - Doloto & Smush.it

Doloto is a JavaScript download optimizer developed by Ben Livshits of Microsoft Research.

Smush.it is an image optimizer. It reports how many bytes would be saved by optimizing the page's images and provides a downloadable zip file with the minimized "lossless" image files.

Are there any other indispensable Web Developement tools that I'm missing?