When me and my wife became parents, around 10 years ago, I tried to document all the nicknames she used to call our daughter. I will not repeat those I still remember because they all were invented by her, and they were meaningless in Hebrew. As for today, when I talk with them by phone, I call them מתוקה (metuká) and מתוקות (metukót). My father in law who is 93 years old, tend to use the Yiddish origin "mámele" (as you can guess - a very old fashion option). For mor trendy option, you'd better ask the young ones here.. ;-)