Fun topic.
Series by series:
TOS/TAS: Uhura, as the username would suggest. Yeoman Rand had some interesting early bits (Enemy Within).
TNG: Beverly Crusher. Tasha was gone too quick and Troi blossomed later on. I did love me some Vash, as well.
DS9. Kira and Jadzia, for sure.
VOY: Kes. Before she went nuts. And Be'lanna.
ENT: T'Pau.
DISCO: Tilly. And all the Georgiou's.
Picard: Tough one. Pill did a great job with Agnes, but she went way too far, character-wise. I do love me some Raffi. But I think I'd go with Seven. And the evil Romulan (she wasn't wrong).
LD: Tendi. What is not to love?
SNW: Really tough here. Chapel & Una are great. But if I had to pick one, I'd go La'an.
PRO: Kids show, so I should not, but Gwyndala.
1 per show: Uhura, Beverly, Jadzia, Kes, T'Pau, Tilly, Seven, Tendi, La'an, Gwyn.
Best others: Kira, Vash, SNW Chapel, Una, Be'lanna, Georgiou, Rand, Narissa, Troi, Raffi.