Alex Sawallich

This plugins enables the famous Google +1-button in your wordpress-installation. The button is shown beneath 
your posts/pages. With this button you can share the permalink to your post/page in your Google+ profile.
You’ve got the possibility to change the look of the button in the same manner, that you can do by using the 
configurator that Google provides: see <a href="http://www.google.com/webmasters/+1/button/" rel="nofollow ugc">Google plus one</a>.

Google+ One Button

Provides a +1 button from Google+ beneath each post/page.

Patrick Chia

This plugin allows you to generate a <a href="https://plus.google.com/" rel="nofollow ugc">Google+</a> favicon for your blog and admin logo included Apple touch icon. Activate the plugin, and it will add G+ photo to your blog template and admin panel automatically.

Google Plus Favicon

Simply add a Google+ account ID to generate a G+ favicon for your blog and admin logo included Apple touch icon.

Google+ One Button vs Google Plus Favicon