Cernocky

The Custom Post Styles plugin is an easy way to customize css of your posts individualy using CSS code. 
Plugin adds css editor box in your post editor.
See it in action: 
https://vimeo.com/179525212
Improve the user experience for your readers without having to change theme code.
<h4>Possible upcoming features</h4>
<ul>
<li>Better CSS editor</li>
<li>Custom webfonts</li>
<li>Supporting more post types</li>
<li>Custom styles for posts by categories, authors etc.</li>
<li>Visual editor</li>
</ul>

Custom Post Styles

Allows you to add custom css styles to posts.

MMDeveloper

A wordpress plugin that lets you search for text within your templates.
Built by The Marketing Mix Perth: https://www.marketingmix.com.au

Search My Theme

I had to fix an issue of broken image paths on a website that I had not developed. The other developers were using an ip-based image path, which broke when the site's IP changed. This plugin let me search for the IP and find where it was being referenced to in the files. It also let me search for a CSS selector. Fantastic plugin, will probably use again!

Custom Post Styles vs Search My Theme