I'll start - Pauline.
Can I only pick one? Caroline
Ondine has been growing on me lately.
Lucienne is one my top ten right now!
Josephine and Marcelline are probably my top two, I'm fond of Segolene as well.
I'm in the minority, but I love Maximilienne (a legitimate French feminine form of Maximilian) for a girl! By far my favorite. I also really like Ondine, Isaline and Lucienne.