The obvious never being beneath me ... Sweetheart.
M'love. Honeybunch. Sweetie-pie. Honeybug. Lover.
And a word I learned from my college roommate "Nudnick" which is a word, I believe, meaning one who drives you to the brink of madness then does something so adorable and sweet and unexpected you simply *have to love them. For example she named her kitten "Nudnick." A lot of young children deserve the appelation too, n'est ce pas, Mothers?