vic-m

JShrink minifier implemented for WordPress. Combines footer scripts equeued by wp_enqueue_script into a single minified js file. Check the FAQ section for more info about the plugin.
Important note: only footer scripts which are equeued by wp_enqueue_script with the fifth parameter set to ‘true’ are minified by this plugin.
JShrink is a php class that minifies javascript so that it can be delivered to the client quicker. Check https://github.com/tedious/JShrink for more info.
Works for sure with: WordPress 4.0+, PHP 5.4+.

WP-JSHRINK

JShrink minifier implemented for WordPress. Combines footer scripts equeued by wp_enqueue_script into a single minified js file.

neoslab

Powered Minifier allow you to reduce your page load and increase your performance by minifying your HTML source along with all the CSS and JS code present in your markup.
<h3>License</h3>
Good news, this plugin is free for everyone! Since it’s released under the GPL, you can use it free of charge on your personal or commercial site.

Powered Minifier

Honestly it's the best minifier plugin for Wordpress 

Simply Excellent

Reduce your page load by minifying your HTML source along with all the CSS and JS code present in your markup.

WP-JSHRINK vs Powered Minifier