MrXHellboy

This plugin offers your visitors the possibility search on post tags. 
All you have to do is install this plugin and create a page and add the following shortcode: [tagsarchive]
The following CSS classes and divisions are added to this plugin so you are able to customize the look in your own stylesheet. 
This because when i update the plugin, no work will be lost on your side.
form#form-search-tags, span.error, form#form-search-tags legend, form#form-search-tags fieldset, span.headings, form#form-search-tags h3
<h3>Development Blog</h3>
<a href="http://online-source.net/category/scripts/wordpress-plugins/" title="Online-Source WordPress plugins" rel="nofollow ugc">Online-Source WordPress plugins</a>
<h3>Development</h3>
Version 1.1: Fixed: error message added if both fields (tagname like and tagname is) are empty. 
Version 1.2: Fixed: shows no tags anymore which have a usage of 0.

Advanced tag search

This plugin offers your visitors the possibility search on post tags.

tommasomeli

Customize WordPress with Global Custom Fields! You can use GCF for example to create HTML + PHP shortcodes, global text fields, to save custom urls and retrieve them wherever you want and much more.
Add global fields in GCF Admin Page Create groups in the ‘Settings’ section and related fields in the ‘Fields’ section. Then edit the fields individually from the ‘GCF’ section.
Recover GCF with php Fields groups / single gcf can be retrieved anywhere within your theme / plugin with the function <code>get_gcf($group, $single = false, $eval = false)</code>
Show single GCF with a shortcode Load and display your single gcf with a shortcode! <code>[gcf group="group_name" field="field_name" eval=false]</code>
Each field is validated before saving. Add non-standard HTML tags and attributes in the “Settings” section if you need.
N.B. Use php “eval” only if you know what you’re doing. Save php fields using pseudo tags <code>[php] ... [/php]</code>
<a href="mailto:info@tommasomeli.it" rel="nofollow ugc">contact</a> me if you have any questions, issues, or suggestions. 
And leave a <a href="https://wordpress.org/support/plugin/global-custom-fields/reviews/#new-post" rel="ugc">review</a> to grow the project!

Global Custom Fields

Create Global Custom fields and save them into WP Options, get them with PHP or use gfc Shortcode

Advanced tag search vs Global Custom Fields