In the first section are standard plug-ins that go on every website, and the second list is honorable mentions that get used frequently for specific purposes. Other than that they are not in any particular order other than alphabetical.
1. Akismet – website
Yes I know this is installed with your Worpdress when you get it, I do recommend you get the key and activate this to prevent spam in your comments section, I find it to be very effective.
2. Better WP Security – website
This plug-in has lots to offer from a security standpoint, it helps to lock down your website and point out security holes.
3. BWP Google XML Sitemaps – website
Creates and maintains an updated sitemap index of all your sitemaps for your Google Webmaster tools so you don’t need to monitor it after the initial setup.
4. Exclude Pages from Navigation – website
I find this plug-in useful for situations where I am using the default page navigation and want to keep certain pages from the main menu (for example a privacy policy which I put in the footer navigation). For more complex menus I will just create custom menus, I do find I use this plug-in frequently though.
5. SEO Rank Reporter – website
A great little plug-in for monitoring how certain keywords are performing in Google. It provides a nice little graph of your top keywords and will let you track how specific pages are performing as well as the entire website.
6. Simple Lightbox – website
A very handy and customizable plug-in for the jquery lightbox function.
7. User Photo – website
A simple way to get your users photos uploaded for their author page and blurb.
8. WordPress SEO by Yoast – website
I use this plug-in for managing my page titles and meta descriptions, is a great Search Engine Optimization (SEO) plug-in.
Those 8 plug-ins are on every WordPress website I create, the next four I use frequently when I need the functionality.
9. Add from Server – website
This plug-in allows you to add files from an external folder on your web server into your WordPress installation. This is handy for when you have an FTP folder for users who do not get access to your WordPress root folder. Also for using FTP to move extremely large files into WordPress (Files WordPress cannot upload as they are too big)
10. NextGEN Gallery – website
A highly customizable and visually appealing image gallery. I searched long and hard through many gallery plug-ins before I found this one and was fully satisfied.
11. qTranslate – website
I love this plug-in for multi language websites, I have used it frequently for French / English websites as well as an English / Inuktitut WordPress website.
12. WPTouch Pro – website
This plug-on creates a mobile version of your existing WordPress website. While I highly recommend that all websites be fully responsive, I realize that sometimes a company has an older WordPress website and are not quite ready to invest the time and money to make it responsive. So in the meantime this plug-in works great to provide cell phone and tablet users a friendly interface to browse your website.
If you can think of any plug-ins that perform better than the ones mentioned above, please share them here. I will try them out and add them to the list if I like them better.