I've never cared for being called "dear," "darling," "honey," "sugar," "sweetie," or "sweetheart" by anyone. (My parents have some pet names for me, but only they are allowed to call me by those names.) Somehow they have always come across to me as condescending and cutesy rather than endearing-especially by adults in professional or other non-personal situations. When I get called those in such situations, I request that the adult call me by my name.
I did get in the habit of calling my youngest niece Little Munchkin, but that was largely because she looked like a Munchkin when she was a newborn-she was very small and very cute. My SIL called her Bug because she has huge eyes (inherited from her mother-I think they're beautiful myself). If my niece ever tells me that she doesn't want to be called Munchkin (or any other nickname), I will stop immediately.