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.
