Faster than a credit card, more powerful than an eWallet solutions, able to leap online protocols with a single check ... it's a direct bank transfer!
Direct bank transfers, a.k.a. wire transfers, represent perhaps the ideal combination of freedom, speed and security for the online casino player, with the sole (tiny) disadvantage being that typically a bank account is needed -- but seriously, who doesn't have a bank account?
As Wikipedia reminds, "Wire transfer systems are intended to provide more individualized transactions" and give the player reassurance that no funny business or hacking is going on, for one must actually physically go and request such a transfer from a financial instuition or cash office.
Many online casinos accept this near-foolproof form of electronic payment and player accounts are generally credited immediately upon reception of the deposit. See a list of casino websites taking direct bank transfers and cash transfers.