Posted by mgifford on December 3, 2013 at 2:09pm
There were some interesting ideas about making sites more fun & engaging - http://mashable.com/2010/04/07/funware-game-mechanics/
Vote Up/Down - support an idea or not - https://drupal.org/project/vote_up_down
Voting Rules - configurable actions based on voting - https://drupal.org/project/voting_rules
Advanced Poll - https://drupal.org/project/advpoll
Quiz - https://drupal.org/project/quiz
Lots of these can be engaged to encourage more interaction & engage users.
I don't know how to best mash these up into a leaderboard mind you.