I came up with a list (you can add to it or mention your opinions if you like) of names that became more popular for boys in years/decades past, but now that their popularity on girls has declined or is declining might be usable on a boy again. This list does not include names which are currently being contested on their gender usage (e.g. [name]Peyton[/name], [name]Riley[/name]). Some of these [name]Pam[/name] and [name]Linda[/name] don’t even consider “unisex” anymore (absence on either or both the unisex list in Beyond [name]Ava[/name] and [name]Aiden[/name] or when using the name search feature on this site with the unisex option), but I think still at least belong in the “unisex” category. Here is the list as of right now (I might think of some more later), some of which I would not rule out for naming a DS of mine in the future if one comes along:
[name]Carey[/name]/[name]Cary[/name] (differentiated from more feminine spellings like [name]Carrie[/name])
[name]Kerry[/name] (see above on [name]Carey[/name]/[name]Cary[/name])
[name]Sidney[/name] (with that spelling)
*Have been used on celebrity sons in recent years (although [name]Kelly[/name] was spelled [name]Kelley[/name] in that case, but both spellings are legit for a boy [name]IMO[/name]).
ETA: The above list might be like a list opposite that of [name]Pam[/name] and [name]Linda[/name]'s “Geezer Names for Girls” list, in that many of the above names sound fresher to some of us when applied to boys.
On the other hand, these names might be tougher to redeem for boys, either because they were never really popular for boys or got very popular for girls at their peak (or both):
[name]Ashley[/name] (in the U.S. or other places where it got really popular for girls but remained low in popularity for boys)