I had a really bad problem with Tango. I tried yelping, which didn't work and I tried giving him other toys that didn't work. I tried two new things recently and he is like a new dog!!
One: when he bites hard, AS SOON AS HE BITES, get up and walk away from him. Don't say a word, don't say no, don't say anything. Just get up, turn your back and walk away. They HATE being ignored.
Two: If he continues and gets totally out of control, put him somewhere for a time out. You can either use his leash and tie him to the stairs, or as I did, I locked him in the bathroom for a few minutes.
I swear, it's been 3 days and he's made a complete turn around!! Now when he puts my hand or fingers in his mouth, there is no pressure whatsoever.
And I"m thanking the puppy-gods because I couldn't take the biting anymore!!