I would guess Gavilar. Bloodrelated to Elhokar and Dalinar, formerly King of Alethkar, keeping a lot of secrets, having this big fall with Szeth and the balcony, being brother of Dalinar and biting the dust for the rest of the story.
Since Shinwarrior is off, I would put this up for discussion. If anyone has a better guess, he/she can have a go, and if you guys agree with me, I'll go ahead and take the next round.
And if anyone disagrees with any of this but has no other guess to solve, we could also just do a freebie round. Anyway, the show must go on!