My least favorite is
Katharine. I like
Katherine (and
Catherine), but still there are a lot of people with this name (usually in the form of
Kate or
Katie) and that makes it seem less classic for some reason.
Elisabeth is sweet, pretty, and classic- but there are so many Elizabeths that it might get annoying having to say "
Elisabeth WITH AN S!!" all the time.
Charlotte is good. I usually oicture it on an older person, but the name has a very friendly and knowledgable vibe.
Rosamund is probably my favorite, because it's classic but not overused and (to me) it has a bit of a medieval vibe.