Maxaud

This plugin allows you to define different CSS rules that get loaded into the page’s for specific devices.
Includes checks for 18 different tablet options and 13 different phone options.
This can be useful if you need to target specific phones or tablets to make CSS changes or show certain advertisements for certain devices.
For more options or if you feel like donating, check out the <a href="http://codecanyon.net/item/mobile-css-pro/3182318/" title="Mobile CSS Pro" rel="nofollow ugc">PRO version of Mobile CSS</a> that is available for purchase.

Mobile CSS

Allows you to define different CSS styles that get loaded for specific mobile devices.

railmedia

Responsive menu based on the Sidr jQuery plugin developed by BERRIART. It features an options panel where the menu can be configured. You can choose between sliding from the left or from the right side of the page, to have a full width bar or a simple button as the menu trigger and more. The menu features two CSS themes: dark and light.
It also adds two sidebars in Appearance -> Widgets, where you can add widgets before and after the menu.

Mobile CSS vs Sidr Responsive Menu