Alex Mansfield

This plugin allows you to easily add code to your pages and posts without worrying about what the WordPress editor will do to it. You can embed HTML, video embed codes, Paypal forms, Google maps and more. Please note: this plugin will not allow you to run server side scripts such as PHP.
To use the plugin, all you have to do is create a custom field (you can name it anything), place your code in the new custom field, and place the following shortcode into your post where you want the code to go:
<pre><code>[easyembed field="name-of-custom-field"]
</code></pre>

Easy Embed

Allows any code to be easily embedded in posts and pages.

Sharaz Shahid

Code Widget is simple widget allows you to insert any arbitrary Text/HTML and run PHP Code or Short Code. This Widget parses PHP code into simple text and much more.
Only users with the unfiltered_html role will be allowed to insert unfiltered HTML. This includes PHP code, so users without admin or editor permissions will not be able to use this to execute code, even if they have widget editing permissions. 
This plugin is developed and maintained by <a href="https://twitter.com/sharazghouri1" rel="nofollow ugc">Sharaz Shahid</a>

Code Widget

Code widget help  to  add  Short Code, PHP Code, HTML, and Simple Text in widget.

Easy Embed vs Code Widget