Ooh that's tough. I think Firo was probably my favourite. Ladd Russo was also amazing as a bad guy. Jacuzzi was cool. Isaac and Miria were hilarious fun, much better written than most comedic relief in serious anime is.

I watched the dub, am so glad I did because of all the accents fitting the setting / ethnicities. Although I do wonder if Japanese have their own variations of accents they use for French/Irish/etc... but I'd not have picked up on them, that's for sure.