Rage clicking is when a user tries to perform an action, and, upon not seen any change in the UI, clicks the same area multiple times. This is a great indicator that the user is expecting something to happen or at least some feedback that his/her action is being processed.
This is a metric you probably want to keep track of, as rage clicking is undesirable for almost any web application. Maybe if you are building a click-based game this would be fine, but for a web application, probably not.
Even if it's not an error, like a user adding multiple identical products to a shopping cart (which could trigger a rage click), it indicates the user is putting a lot of energy into the action.
So go ahead, pick your poison. Do you want free money? Would you like 1 BTC? Perhaps adoptin a unicorn? Whatever you want. Click on your favorite button and see what happens. 3 quick clicks trigger the rage effect!