Hello, I got an American Express gift card worth $50.00. I went to go add some of it to my eShop account, but the only 3 types of cards I can use are 3DS prepayed cards, Visa, and Master Card. I am sad and I am wondering why only Visa and Master Card are only availible.
I would go buy a prepayed card, but there is tax, and I don't have time to go to the store and buy one........
You can buy a 3DS eShop gift card with your American Express gift-card. Most cashiers will be able to apply the first $50 dollars to the American Express card and then anything extra (i.e. the dollar or two of tax) can be paid in cash or with another card.
Simple. Because at this time, that's simply all Nintendo accepts for the purchasing funds using the Wii Shop Channel, Nintendo DSi Shop, and the Nintendo eShop.
However, do be aware that not all places charge tax on a prepaid card. Some stores may not charge tax, while in other cases, some states don't charge tax on prepaid cards of any kind. If it'll make you feel better, and if you're a collector of Nintendo items, there is the Limited Edition The Legend of Zelda 3DS Prepaid Card that is currently available, featuring the image of Link battling Ganondorf, as seen in The Legend of Zelda: The Ocarina of Time. If you're a collector, don't worry about the tax.
There is no knowing why Nintendo only decided to support Visa and Mastercard. You can ask them directly with their webform: http://www.nintendo.com/consumer/webform.jsp
There is also tax on individual purchases that you make on the eShop (depending on where you live), regardless of whether you added funds with a prepaid card or credit card.