I've always been a fan of Thranduil (as well as Lee Pace,) and that interest only grew once I saw The Desolation of Smaug. If he'd had more screen time in AUE, I probably would have taken him up a while ago. In general, I think Thranduil is very interesting. While other elves, such as those in Rivendell, could be seen as light, beautiful, gleaming beings, those of Mirkwood are a bit.. darker. That, alone, fascinates me, as well as Thranduil's background, in general. He's wise, he's endured many terrible things, and that's all formed him into the king he is now.
He has a very angsty history. Where do I even start -- I don't quite know how to explain it, but I suppose his overall attitude is great, to me. He's wild in the sense that he's like a wolf or a hurricane.. yet he still cherishes family (what's left of his, at least) and is protective of his people. I just wish there was more known about Thranduil.