What's in your Testers Tool Box?

The test interview is not only a test of interviewee specific knowledge, but an opportunity to knowledge exchange. As an interviewer I have to spend at least half an hour interviewing some potential Quality Assurance Engineer and I want to use these minutes wisely. For example, I like to interview testers about various tools they use during preparation and actual testing. Here are some wonderful tools I use in my day-to-day testing routine:

Firebug - extension for Mozilla Firefox browser allows the debugging, editing, and monitoring of any website's CSS, HTML, DOM, and JavaScript;

YSlow for Firebug - helps QA Tester to analyzes web page performance by examining all the components on the page and even gives suggestions on how to make it faster;

Web Developer toolbar for Mozilla Firefox - makes CSS, HTML and link validations right from your menu bar;

Selenium - a free software testing framework for web applications;

Windows Virtual PC - is a virtualization suite for Microsoft Windows operating systems, and an emulation suite for Mac OS X on PowerPC-based systems. Virtual PC allows you create separate virtual machines on your Windows desktop;

Cygwin - a Unix-like environment and command-line interface for Microsoft Windows;

OpenSTA - GUI-based web server benchmarking utility that can perform scripted HTTP and HTTPS heavy load tests with performance measurements;

WinSCP - an open source SFTP and FTP client for Microsoft Windows;

HttpWatch – an HTTP Viewer and HTTP Sniffer for IE and Firefox;

Do you use any other good tools?