What Tools and Extensions are Critical for Magento Development?

We're building a nice little community of Magento experts here. I'm curious what Magento extensions and other software tools (IDEs, editors, etc.) everyone is using to help with their development projects?

Both free and commercial tools are more than welcome.

Personal developer surely need

• PHP IDE (Zend Studio, NetBeans or PhpStorm)
• LAMP/WAMP on personal development machine
• X-Debug as a must
• MySQL client (HeidiSQL)
• Firefox + FireBug as main browser; Safari 4/5, Chrome, Opera 10, IE 6/7/8/9
• SSH Client (PuTTY)
• FTP Client and File manager over SSH (WinSCP)
• Manuals for PHP, MySQL, Javascript and Prototype
• Bug tracking system (Jira)
• SVN to keep own revisions and be in touch with future Magento release from at magentocommerce.com
• KDiff3 for SVN better sources comparison
• Image Viewer (XnView) to work with images from time to time
• Password keeper (PwSafe) for all hostings, mysqls and other passwords
• Internet access for Q&A, Magento forums and tutorials

No custom extensions are really necessary, X-Debug and own experience help a lot. For beginners Commerce Bug will be helpful.