This is more akin to financial arbitrage but my mother did a variant of this for her car payment. The card company would send her 'checks' to use for 0% balance tansfers that she would get 5% rewards on. So she'd use the checks for her 3.9% car payment, get the rewards and pay off the card at the end of the month.
I remember going to the casino and taking out a $5000 cash advance and then paying it back the same night. For about $2 in interest you got 5000 aeroplan, or air miles. I did that each weekend for 20 weeks until I got enough miles for my trip to Australia.