I like
Marian! Mostly because of
Robin Hood too, it gives me a medeival feel because of it :)
Marion is okayish, but I much prefer
Marian. Also, I've met a boy named
Marion, so I think of
Marian as "girl" and
Marion as "unisex". Plus
Marion doesn't have the association of Maid
Marian.
I don't think people would spell it like that too often. It might be a regional thing (right now I'm going to school in Iowa, fairly near to a city called
Marion. So if I introduced myself as
Marian here I might get a few
Marion spellings because of that, but I think
Marian would be more popilar in other places.)
I don't think
Marianne is all that similar to
Marian, actually.
Marianne seems like more of a
Mary Anne mashup, and it has a completely different feel despite having "
Marian" in it.
I'd be happy to see it. I'd like it with a middle name that made me think "medeival" in some way, or maybe a naturey one.
Marian Cecily,
Marian Siobhan,
Marian Ivy,
Marian Wren,
Marian Guinevere (too much?)