The Ranking Block is a new addon at Moodle.org that is designed to enhance the gamification of your course through completion and grades. Developed/maintained by William Mano the block uses course completion activities and grades to aggregate a formal ranking of students and puts that information on display. Point defaults can be customized as can which activities and resources help to contribute to the ranking points accumulated. This is all collected up to a course ranking block (similar to a quiz ranking block) within the course.
Check out the block at Moodle.org: https://moodle.org/plugins/view.php?plugin=block_ranking It is available for Moodle 2.2 and up.
To see how the block works you can follow along with William’s tutorial (8 minutes) here: https://www.youtube.com/watch?v=bxbG1nLtZ_Q