Flector

You can use this plugin to hide part of the text of a post in a nicely-formatted container that will becomes unhidden when clicked on. The plugin can be useful for creating FAQ pages, hiding large pictures, and things like that.
The plugin creates its own “Spoiler” button in the visual editor, but you can also add spoilers directly using tags. For example:
<pre><code>[spoiler title='Title']Spoiler content[/spoiler]
</code></pre>
or
<pre><code>[spoiler title='Title' collapse_link='no']Spoiler content[/spoiler]
</code></pre>
If you liked my plugin, please rate it.

BBSpoiler

This plugin allows you to hide text under the tags [spoiler]your text[/spoiler].

Rafael Mardojai CM

Use responsives alert boxes with shortcodes. 
Is easy, only use the shortcode.
Example: For a info message use: 
 [alert type=”success”]Your text here[/alert] 
Also you can change the icon size: 
 [alert type=”success” icon-size=”big”]Your text here[/alert]
Shortcode attributes:
<ul>
<li>
type (defines the style of the alert box):
<ul>
<li>info (display a info style box)</li>
<li>success (display a success style box)</li>
<li>warning (display a warning style box)</li>
<li>danger (display a danger style box)</li>
</ul>
</li>
<li>
icon_size (defines the icon size):
<ul>
<li>normal (icon normal size)</li>
<li>small (icon small size)</li>
<li>big (icon big size)</li>
<li>hide-icon (no display the icon)</li>
</ul>
[alert type=”type” icon-size=”icon-size”]Your text here[/alert]
</li>
</ul>
<ul>
<li>Demo & Examples: http://www.rafael.mardojai.com/simple-alert-boxes-plugin/</li>
<li>Github repository: https://github.com/mardojai/Simple-Alert-Boxes-Wordpress-Plugin</li>
</ul>

Simple Alert Boxes

Nice

Use responsives alert boxes with shortcodes.

BBSpoiler vs Simple Alert Boxes