Had to change my answer to now say that Askin Nakk Le Vaar is my favourite so far. I always found him to be an interesting character among the Sternritter and I was pleasantly surprised oleh his revealed schrift, "link" and it's unique style of ability.
Liltotto Lamperd, as far as personality and character design. She's competent, but not deliberately out of place like most of the others. In fact, though this is not saying much, I think she has the fullest 'character' out of all the Sternritter.