What are your favorite in game characters?

[Lauront]

ARR: Lahabrea, Jacke, Brithael, Gaius, Livia, Riol.
HW: Regula, Varis, Ysayle
SB: Hien, Yotsuyu, Magnai, Daidukul
ShB: Emet-Selch, Thancred, Vauthry, Ardbert
EW: Jullus, Hythlodaeus, Sicard

I'm likely forgetting someone and any character mentioned can typically carry over into subsequent expansions if and when they have additional scenes.

I'd agree with the entirety of this list. I'd add Elidibus to ARR (and beyond), as well as Nabriales, and Estinien, Hraesvelgr, Igeoyrhm and Ardbert to HW. I'll also admit to enjoying Zenos back in SB... but not beyond that. Misija as far as SHB is concerned is another fave. So far I'm not too enamoured with Vrtra but that may change later.