For girls, anything that’s stronger and more substantial, and less frilly/cutesy/twee than most of the current crop of popular names. At the moment it feels like most parents of girls are terrified of vowels!
Lots of underused Shakespearean names also deserve a revival imo:
Miranda
Marina
Rosalind
Helena
Celia
Juliet (think this one’s already making a comeback)
For boys, lots of the New Testament names already mentioned (Simon, Peter, Christopher, Matthew) plus some of the Old English and medieval names: Edmund, Edgar, Ambrose etc.
More Scandi/Nordic style names for both sexes: Frida, Thora, Asta, Magnus, Gustav, Stellan, Soren.