Stephen AfamO

This plugin allows you to use any HTML or PHP file as the template for any page or post.
Simply upload the file and select it. 
You can upload custom js and css files into the media library and link to them from the HTML file.
Options:
<ul>
<li>Overwrite All: You overwrite the entire theme and use your custom file</li>
<li>Overwrite Content: Keeps the header, footer, sidebar, e.t.c. Simply overwrites the body of the page or post</li>
<li>Above Content: Your custom content is simply added to the top of the page content</li>
<li>Below Content: You custom content is placed just beneath the page content.</li>
</ul>
<h4>Adding support for custom post types</h4>
By default the pulugin works with pages and posts, however, go to the settings to enable it on any other registered post type.
use the <code>hppp_post_types</code> filter to add more post types.
Like this:
<pre><code> public function post_type_modify ($post_types) {
 $post_types[] = 'custom_post_type';
 return $post_types;
 }

 add_filter( 'hppp_post_types', 'post_type_modify' );
</code></pre>

Custom HTML/PHP Post Templates

I use this on a couple sites I own and it works wonderfully.
I hope you can find it useful. 

Works like a charm

Use your HTML or PHP files for any page or post.

Jackson Whelan

Taxonomy Templates allows user selection of a theme’s available taxonomy templates, much like how pages can select their template.
When additional templates are available, a drop down appears on the edit Category, Tag and any custom taxonomy pages.

Taxonomy Templates

Taxonomy Templates allows user selection of a theme's available taxonomy archive templates, much like how pages can select their template.

Custom HTML/PHP Post Templates vs Taxonomy Templates