First of all, no offense to other half-deaf people. Just my sister.
1) When we are in the car, I play the name game. While this could have a different meaning to people with normal hearing, for my sister it is played like this: Start saying her name very quietly and keep saying it louder and louder. And then when she hears it, you yell "OMG NEW WORLD RECORD!"
2) When I walk past her, I've found out I can just blurt out any cuss word in front of her and she either doesn't hear it or nods and smiles.
3) I like to call our house phone and watch as she sits at her computer, completely oblivious to the fact that there is a very loud ringing going on. Then when I tell her the phone is ringing, she either doesn't hear it or nods and smiles.
Just thought I would explain to you how I treat my half-deaf sister. Just imagine the fun when she completely can't hear.