I answer to Miss, Mrs and Ms, as I think there's a case for all three (and after all, all three are an abbreviation of Mistress). I accept Miss, because I'm an unmarried woman; and Mrs, because at one time - certainly up to the seventeenth century - that was the form of address for all women, married or not, and I think that's a sensible practice (cf modern use of Frau for a woman and Fraulein for a girl); and Ms as that's the current convention. If pressed, I generally go for Miss, but I'd rather skip titles altogether and stick with forename (or initials) plus surname.

I found out recently that the reason why my brother always uses forename plus surname in emails - which does seem a bit odd between siblings - is that his Quaker school taught him that that formula addressed the whole person.