Easily apply templates to your category archive pages and posts with this plugin.
Valid templates are files placed your theme folder with the following code at the beginning of them:
For Post Templates: Template Name: Blog Template
For Archive Templates: Archive Template: Blog Template
Through this plugin’s options panel, you can choose which templates are applied to categories and posts. Even choose their priority over one another. You can even apply a template to an individual post. 
Please <a href="http://aarongloege.com/blog/web-development/wordpress/plugins/wordpress-plugin-category-templates/#respond" rel="nofollow ugc">report any bugs</a> you come across.
Enjoy!

Category Templates

Give your categories and posts their own individual templates.

Barry Kooij

Never5

What The File adds an option to your toolbar showing what file and template parts are used to display the page you’re currently viewing.
You can click the file name to directly edit it through the theme editor, though I don’t recommend this for bigger changes.
What The File supports BuddyPress and Roots Theme based themes.
More information can be found <a href='http://www.barrykooij.com/what-the-file/' rel="nofollow ugc">here</a>.
<h4>Looking for a great related posts plugin for WordPress?</h4>
Another plugin I’ve built, that I’m very proud of is Related Posts for WordPress. Related Posts for WordPress offers you the ability to link related posts to each other with just 1 click! And it’s 100% free! <a href="https://wordpress.org/plugins/related-posts-for-wp/" rel="ugc">Check it out on the WordPress repository.</a>

What The File

This is great plugin to check templates file. It saves a lot of development time with 100% accuracy for me. Thanks to the developers team who worked for this plugin. Every WordPress developer should have this installed during development tier of their website.

Simple, but superb plugin

cool. very helpful !!!!

What The File is the best tool to find out what template parts are used to display the page you're currently viewing!

Category Templates vs What The File