GKauten

Disables a collection of WordPress features that can help your blog run more efficiently and smoother. 
This includes functions such as the auto-save and revision tracking features used on the post and page 
editor sections which can help reduce database size by eliminating the build up of revisions which exist 
purely for administrative purposes and reduce server load. Other functions include the comment author URL, 
WordPress ‘Generator’ tag, and more.
Special thanks to John Blackbourn (http://johnblackbourn.com/) for his explorations of the Core Update system.

WP Feature Disable

Disables a collection of WordPress features that can help your blog run more efficiently and smoother.

vicchi

This plugin allows you to manage and load site specific functions, scripts and CSS files into your WordPress site without the need to edit your theme’s <code>functions.php</code> or any other source file.
Settings and options include:
<ol>
<li>Choose the type of customization you want to load; functions, scripts, CSS in any combination.</li>
<li>Choose where you want the customizations to load; in the WordPress front-end, in the WordPress admin screens or both.</li>
<li>Choose where you want to store your customization files, without the need to add to or modify your theme’s or your plugin’s source files.</li>
</ol>
<h3>Filter Support And Usage</h3>
WP Customizer supports multiple filters; the plugin’s filters allow you to
<ul>
<li>modify the set of functions files that are about to be loaded</li>
<li>modify the set of script files that are about to be loaded</li>
<li>modify the characteristics of each script file that is about to be loaded and which will be passed as arguments to <a href="https://codex.wordpress.org/Function_Reference/wp_enqueue_script" rel="nofollow ugc"><code>wp_enqueue_script</code></a></li>
<li>modify the set of CSS files that are about to be loaded</li>
<li>modify the characteristics of each CSS file that is about to be loaded and which will be passed as arguments to <a href="https://codex.wordpress.org/Function_Reference/wp_enqueue_style" rel="nofollow ugc"><code>wp_enqueue_style</code></a></li>
</ul>
Each filter will be only be called if the customization type is enabled in the plugin’s options; if a customization type is enabled but no files are found to be loaded, the filter will still be called but will be passed an empty argument.
As with all WordPress filters, any filter hook function should either return the modified argument or the original argument if no modification were made.
<h4>wp_customizer_functions, wp_customizer_admin_functions, wp_customizer_common_functions</h4>
The functions filters are called when preparing to load the list of front-end functions (<code>wp_customizer_functions</code>), of admin functions (<code>wp_customizer_admin_functions</code>) and of common functions (<code>wp_customizer_common_functions</code>). The arguments that each filter hook function receives is identical in all cases. The filter hook function takes a single argument which is an array of file names.
Example: Prevent all function files from loading by returning an empty file list.
<pre><code>add_filter('wp_customizer_functions', 'function_handler', 10, 1);

function function_handler($files) {
 // $files = array(
 // array(
 // 'file' => (absolute path of function file)
 // ),
 // array(...)
 // );

 return array();
}
</code></pre>
<h4>wp_customizer_scripts, wp_customizer_admin_scripts, wp_customizer_common_scripts</h4>
The scripts filters are called when preparing to load the list of front-end scripts (<code>wp_customizer_scripts</code>), of admin scripts (<code>wp_customizer_admin_scripts</code>) and of common scripts (<code>wp_customizer_common_scripts</code>). The arguments that each filter hook function receives is identical in all cases. The filter hook function takes a single argument which is an array of file details.
Example: Add jQuery as a dependency to all scripts and enable each script to load in the post’s footer.
<pre><code>add_filter('wp_customizer_scripts', 'script_handler', 10, 1);

function script_handler($files) {
 // $files = array(
 // array(
 // 'file' => (absolute path of script file),
 // 'handle' => (auto-generated handle for script),
 // 'src' => (URL of script file),
 // 'deps' => (dependencies, defaults to an empty array),
 // 'ver' => (version, defaults to false),
 // 'in_footer' => (load in footer, defaults to false),
 // ),
 // array(...)
 // );

 foreach ($files as $file) {
 $file['deps'] = array('jquery');
 $file['in_footer'] = true;
 }

 return $files;
}
</code></pre>
<h4>wp_customizer_css, wp_customizer_admin_css, wp_customizer_common_css</h4>
The CSS filters are called when preparing to load the list of front-end CSS (<code>wp_customizer_css</code>), of admin CSS (<code>wp_customizer_admin_css</code>) and of common CSS (<code>wp_customizer_common_css</code>). The arguments that each filter hook function receives is identical in all cases. The filter hook function takes a single argument which is an array of file details.
Example: Override the media type for all CSS files to use the <code>screen</code> media type.
<pre><code>add_filter('wp_customizer_css', 'css_handler', 10, 1);

function css_handler($files) {
 // $files = array(
 // array(
 // 'file' => (absolute path of css file),
 // 'handle' => (auto-generated handle for CSS),
 // 'src' => (URL of CSS file),
 // 'deps' => (dependencies, defaults to an empty array),
 // 'ver' => (version, defaults to false),
 // 'media' => (media type, defaults to 'all')
 // ),
 // array(...)
 // );

 foreach ($files as $file) {
 $file['media'] = 'screen';
 }

 return $files;
}
</code></pre>

WP Customizer

It's been three years since this was last updated and it's still going strong, I really hope the author will keep up its development.

I use this plugin to change all kinds of CSS features that otherwise I'd have no clue how to change, the interface is simple yet incredibly powerfull, if it stops working I@ll be in big trouble!

Superb Plugin - well recomended

Easily load site specific functions, scripts and CSS files into your site without editing your theme's functions.php or other source files.

WP Feature Disable vs WP Customizer