The "OW!" tactic works for most.
You said it's ok if he nibbles on your hands or whatever... My guys are like that too, they are allowed to play bite, when we wrestle and such, it's just like when I grab Roxy's neck or whatever with my arms, her mouth is the only way for her to do the same to me. So I allow it.
BUT, if he bites you somewhere he's not allowed or too hard, a sharp "OW!" or "OUCH!" should deter him from biting that hard or that place again.
Usually they'll give you a funny look, like "What's wrong with you?" and stop.
If that doesn't work, usually ending the play session sends them the message. If I bite mommy hard, or in the face (
) we don't get to play anymore. Hrmph. Maybe I won't bite her there because I love to play with mommy!