One of my first jobs after finishing university was at an online electronics retailer in the customer service department. They implemented a new rewards system to "motivate" the workers to handle a bigger amount of emails each day.

It worked like this: everytime you got an email where the customer wanted to return a purchased product for whatever reason, you could send a template offering a 20% discount if the customer kept the item instead. Even just offering this discount gave the employee who handled the email a small amount of money added to this monthly paycheck. If the customer then also decided to accept the offer and keep the item for the 20% discount then we would get even more money added to our salary.

After looking through the options in the emailclient we used, I found a way to see the "qued" emails that were assigned to me. There was usually no apparent way to alter the emails that were assigned to you so you'd just press "next" after finishing an email and then you'd get the next one at random. This way I could "force" the client to hand me a certain email that was somewhere in the que, so obviously I would pick the ones that ended up giving me money. If all emails worth cash in the que were gone, I would just restart the client and get assigned a new set of emails :D Rinse and repeat! This way I easily made around 400-500 euros more a month.

Every morning all customer service employees would get a list sent to them with a form of "leaderboard" where you could see who had earned the most money this way. I always made sure to not make it too obvious that was I cheating the system by staying in the top 3 of the leaderboards and not overdoing it.