Cash back is the most popular type of credit card reward. According to creditcards-dot-com, 49-percent of U.S. adults have at least one cash back credit card, up from 43-percent last year. This is way ahead of the second most favorite card, the gas or retail card. Only 29-percent of U.S. adults have this sort of card. When it comes to redeeming rewards, the cash back cardholders are more likely to redeem theirs. Of those surveyed, 88-percent reported redeeming their rewards at least once compared with only 43-percent of gas and retail card holders.