-Churn unlimited Citi AA cards.
-Get AA Platinum status for accumulating miles from above credit cards
-Churn unlimited Amex cards for bonuses, and then ask them to match those bonuses to better ones.
-Churn unlimited Chase cards for bonuses. (maybe even ask them to match to better bonuses).
-Probably have SBS
-Feel free to add your own...
(of course, most of us probably would never know these things existed...)