For everything I buy, including stocks (from Loyal3.com). Even without the minimum 2% cash back we get (Barclaycard Arrival+), the benefits and fraud protection are great. I've made over $1,000 in cash back so far this year. Although my wife gets cash tips at her job, I prefer she uses a credit card whenever she can instead of the cash. Easier to track on Mint.com and I like the cash back!