So here is my list, I would love to see what you all use on your wordpress sites.
1) Google Analyticator
Adds the necessary JavaScript code to enable Google’s Analytics. After enabling this plugin visit the options page and enter your Google Analytics’ UID and enable logging.
2) Google XML Sitemap
This plugin will generate a sitemaps.org compatible sitemap of your WordPress blog which is supported by Ask.com, Google, MSN Search and YAHOO.
3) All in One SEO Pack
Out-of-the-box
SEO for your Wordpress blog.
4) cforms 10.1
cformsII offers unparalleled flexibility in deploying contact forms across your blog. Features include: comprehensive SPAM protection, Ajax support, Backup & Restore, Multi-Recipients, Role Manager support, Database tracking and many more.
5) Add to Any: Share/Save/Bookmark Button
Helps readers share, save, bookmark, and email your posts and pages using any service.
6) Tweet This
Adds a Post to Twitter bird icon to the top-right of every post and page, with a nice rollover effect. Shortens URLs in advance through Th8.us, eating up only 16 of 140 characters. Customize or disable auto-insertion under Settings > Tweet This.
7) My Page Order
My Page Order allows you to set the order of pages through a drag and drop interface. The default method of setting the order page by page is extremely clumsy, especially with a large number of pages.
8) TinyMCE Advanced
Enables advanced features and plugins in TinyMCE.
9) WP-Cumulus
Flash based Tag Cloud for WordPress
10) Lightbox 2
Used to overlay images on the current page. Lightbox
JS v2.04