My mom dated a [name]Brooke[/name] once. 
Erm, I know on the SSA list around the turn of the century, a lot of vintagey/classic girls’ names ([name]Ivy[/name], [name]Anna[/name], [name]Pearl[/name], [name]Katherine[/name], etc.) all ranked in the lower half of the SSA list for boys.
As for legitimate girls’ names (and not unisex ones like [name]Avery[/name], [name]Bailey[/name], [name]Taylor[/name], [name]Emerson[/name], [name]Aubrey[/name], etc.) that could work on girls, maybe [name]Hero[/name]? I know it’s traditionally a girls’ name, was used by [name]Shakespeare[/name] for a girl, but I don’t know why it couldn’t be used for a boy. A lot of nature/virtue names could be like this, too, but then I guess that would make them more unisex, since they don’t have any gender in English. Hmm, I guess some of the -et names could cross over to the boys, since there are so many for both genders. But honestly, I see [name]Emmett[/name], [name]Everett[/name], [name]Elliot[/name], [name]Bennett[/name], etc. crossing over to the girls way before [name]Juliet[/name], [name]Violet[/name], [name]Charlotte[/name], [name]Ayelet[/name], Adalet, [name]Lisette[/name], etc., would ever be considered on a boy!
Maybe some -o ending names, too. Like [name]Cleo[/name], [name]Echo[/name], [name]Calisto[/name]/[name]Calypso[/name]/[name]Callisto[/name]/etc., [name]Cameo[/name], [name]Dido[/name], Emiko, [name]Io[/name], [name]Juno[/name], [name]Kato[/name] (saw it listed somewhere as a form of [name]Katherine[/name], but I can easily see it being confused for the masculine [name]Cato[/name]!), [name]Margo[/name]/[name]Margot[/name], [name]Mio[/name] (looks more like the masculine word for “mine” in Spanish, rather than a feminine Japanese name, to me, though), [name]Rosario[/name] (I always thought this looked masculine, anyway!), etc.
I also saw [name]Picabo[/name] (like the child’s game) listed as a girls’ name, but if it were used (which I definitely wouldn’t recommend! lol), I think it sounds more masculine.
I could sort of see [name]Eliza[/name] being used on boys, too, since it sounds so close to [name]Elijah[/name].