WP Social SEO Booster
Takes care of all the microdata and other things that are needed to ensure your post looks right on various social networks
A security plugin that enhances a number of things and prevent several different hacks. I have had problems with other popular security plugins, so I now only use Wordfence. There is also a caching functionality in Wordfence, but do not have to turn it on if you already have another caching plugin, although it is quite effective considering the super simple setup.
UpdraftPlus – Backup/Restore
A really good backup plugin that can also backup to various third party services such as Dropbox, Google drive, Amazon and other. It is the most reliable free backup solution I have tried so far
This is absolutely one of my favourite services. This allows you to monitor and update multiple sites at once and have saved me so much time. Another advantage is that you do not risk missing an update of one of your sites
This is not a plugin I use very often, but it is indispensable when I need it. It regenerates the image sizes which is very useful when you change theme or make changes to an existing theme
WordPress SEO by Yoast
This one is a very popular SEO plugin, so you probably already know about it… just remember to actually use it and create some killer Titles and meta descriptions.
Delete Custom Fields
This is one of those plugins that most will probably never need, but what it does is delete old custom fields that you no longer use.
Widget Context / Widget Logic
Both of these plugins are used to control which pages a widget will be shown on. I use both of them on various sites.
WP Htaccess Editor
As the name suggest this plugin lets you edit the Htaccess file directly from the WordPress backend. It also includes an option to backup the Htaccess file before you make changes. Remember to be very careful when messing around with the htaccess file.
W3 Total Cache / WP Super Cache
I use a caching plugin all all my sites. My favourite is W3 Total Cache as it is very comprehensive, however I have had compatibility problems on some sites as it prevented proper detection of mobile devices. On these sites I have used either WP super cache or for some simpler sites just the built in caching in Wordfence.
This is the commentary spam plugin that comes with WP out of the box. I usually do not activate until spam actually becomes a problem. For some reason i have sites that never get any spam, and others that get insane amount of spam comments every day.
Genesis specific plugins
The following are plugins that are made especially for the Genesis theme framework
Genesis Simple Hooks
Genesis Simple Edits