wondermill

If you want to graphically display a random list of your posts with their featured image in the side bar, then this is the plugin for you. This plugin allows you to set the category IDs (or all categories) you want to pull the random posts from, the number of random posts to display, the maximum width and height of the featured image thumbnail, the widget title, and the colors of the surrounding box.

Random Posts with Thumbnails

Puts a list of clickable random posts with their featured image in your sidebar as a widget, this list is customizable.

Scribit

With Random plugin you can insert into your WordPress website one or more random contents coming from your posts. 
The source contents can be pages, posts or custom post types. 
You can display information in many different ways: 
* A list of post titles 
* One or more full contents or excerpts 
* Raw URLs to posts permalink

Random

This plugin give to your website the possibility to get random content for specific posts types. You can use to give to your visitors random posts, or random woocommerce products for your clients.
Very useful in my opinion.

Wikipedia style!

Random, a great plugin designed to insert random contents, posts and other types, into your website. Enjoy its shortcodes!

Random Posts with Thumbnails vs Random