Alien Express Card
I like to think that the little green men have evolved beyond the use of credit cards, but lets face it, they like to steal cows and give people anal probes. So maybe they aren't the paragons of intelligence that scientists give them credit for.
Speaking of credit, these cards are good all over the galaxy. We DO NOT recommend that you replace your mom's AMEX with this and snicker when she embarrasses herself at Costco.