I have a bank and credit card linked to mine and it works fine there, but when using codes like the recent 99INDY .99 deal it makes me pay by credit card like mis_chiff says.
Godaddy used to allow PayPal as a payment option for those promo code purchases but many people gamed the system by opening multiple Godaddy and PayPal accounts.
It's much harder to game the system using credit and debit cards since each can only be used once.
Get yourself a PayPal debit card and you can use that as a work around
to pay for the special Godaddy promo code domains.