I know its hard and you think that nothing is working but I have to tell you IT DOES GET BETTER!
Nikko was a little vampire when he was a baby. He would cling on to our legs and bite our feet. He was constantly biting our hands and it didn't help that my fiancee played rough with him. However, after the teething is over, it does get better. I would hold his mouth shut until he whimpered a bit and said NO BITE in a firm voice while looking into his eyes. Now at 10 months he has mellowed out greatly and if occassionally he gets carried away with the playing I tell him NO BITE without holding his mouth shut and he knows what I mean and responds quickly.