Joel

This is an extremely simple plugin (one line of code!) that deletes all domain cookies whenever a user logs out of your WordPress site, and then redirects the user to the site homepage.
Why? Because by default, WordPress sets a number of cookies that it doesn’t remove on its own when you log out.
There are security and privacy benefits, because if there are vulnerabilities in WordPress or in your browser, or if someone has access to your computer or device, they may be able to access these cookies. (That goes for you or for anyone who logs into your site to add a post or comment.)
Likewise, when a user logs out of your site using a public or shared computer, there won’t be any domain cookies left behind.
The plugin also gives you back the “regular user view” of your site, because after you log out you can browse your site as an anonymous user, without having to manually clear cookies in your browser. (There are many plugins that will display different content or show cached or uncached versions of pages if they see that WordPress cookies have been set.)

Logout Clear Cookies

Clears all domain cookies on logout. Because leaving a trail of cookies is bad.

ecoal95

cmoral3s

Based on the JavaScript version by <a href="https://github.com/ecoal95/CookieTool/" rel="nofollow ugc">Emilio Cobos</a> . 
This plugin shows a notice to your users warning them about the use of cookies in your site. It prevents (some) code to store cookies before user consent. It also shows a link to your (mandatory) privacy/cookie policy page.

WP Cookie Tool

Easy way to follow the EU Cookie directive, especially for Spain (more restrictive law).

Logout Clear Cookies vs WP Cookie Tool