I'm not interested in debit cards; I want the security that credit cards provide if a naughty hacker steals my credit card number.
Which credit cards do merchants prefer to take? In other words, which ones have the lowest rate the merchant is charged, which are "nicest" for the merchant, etc? Right now I have an American Express that I mostly use, but I'm starting to feel bad about making the merchant pay a high fee for me buying their stuff. If possible, I'd like to be nice to them.