The King and the Clown was SO sad, ugh. But I agree, Lee Joongi is great in it. I also really enjoy him in The Scholar Who Walks The Night, but I'm weak for vampires. Flower of Evil was too scary for me, I've never finished it.

Also, there's a Korean textbook to which he recorded the dialogues etc. I used it on one course, before watching his dramas, and didn't really like the choice of the book just for k-ent value. ... unfortunately, after watching some of his dramas, I'm also a fan now xD