I guess it would have to be a tie between my mother and my sister.
Since the divorce, us women have grown really close and I hope it stays that way.
Of course every daughter "hates" their mother during those good ol' teenage years, but I am and have always been able to talk to my mom about anything. Even now, I know I can call her and she will drop everything for me. She even drove 50 miles out of her way to bring me my spare key after I locked myself out of my car.
I hate that I moved away and that I don't see them every day anymore. They tell me about things they do and even the arguments they have. I miss it all.