I like the debit card from my credit union, but nobody outside my country would accept it because it's not affiliated to any payment network like Visa or Master Card.

Other popular payment methods are mobile payment networks provided by the same companies that provide the cell phone service. It's a pre-paid phone service that lets you use your phone credit (that which originally only let you buy talk minutes and text messages) and transfer it to a different phone number. Lots of people accept it as actual currency, and you can even pay utilities with that.