Thumbs Rating does what you'd expect. It allows you to add a thumbs up/down to your content (posts, pages, custom post types...).
It do what he must, but little bit complicate install.
This is a great plugin. It's lightweight, simple, modern design, highly customizable, and easy to use.
For those that want to know, the shortcode to get the top voted posts to show in a list without the vote count displaying, use this (works in widget too):
[thumbs_rating_top post_type="post" show_votes="no"]
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