Haris Zulfiqar

WordPress tooltip plugins lets you add tooltips to plain text and links on your post and pages.
It offers a tinyMCE shortcode GUI which will guide you through the entire process of a tooltip.
This plugin uses jQuery tipTip authored by Drew Wilson http://code.drewwilson.com/entry/tiptip-jquery-plugin.
You can also add tooltips manually by following the pattern below:
<pre><code>[tooltip content="This will show in a tooltip" url="This will make tooltip a link"]Hover over me for tooltip[/tooltip]
</code></pre>
Url is optional. If URL is added, it will render a link otherwise it will be a plain text.

WordPress Tooltip

WordPress tooltip lets you add tooltips to content on your posts and pages.

ClevelandWebDeveloper

Easily add tooltips to your wordpress site. Tooltips will show when target element is hovered over. On mobile devices tooltips show when target element is tapped. You can easily pick your tooltip color settings in Settings > Simple Tooltips.
<h4>How to Use</h4>
To define a tooltip (new, easy way): Click the tooltip icon on your visual content editor to add the tooltip shortcode. Change the content attribute to whatever you want to be the content inside the tooltip bubble. Change the tooltip trigger to whatever content you want to be used to trigger the tooltip, when hovered. (see screenshots)
To define a tooltip (old way): Add class “tooltips” to the target html element. The title attribute will be used for tooltip content.
<h4>Credits</h4>
Thanks to Stefan Gabos who made the original <a href="http://stefangabos.ro/jquery/zebra-tooltips/" rel="nofollow ugc">jQuery plugin</a>.

Simple Tooltips

I was seeking a tooltip plugin for images and this one makes it simple!  Others?  Not so much!  5 Stars all the way!  Thanks!

Easiest tooltip solution

Easily add tooltips to your wordpress site.

WordPress Tooltip vs Simple Tooltips