Koenma is kinda cool in the original comic, but very stupid on the anime (I'm sorry to say, but its true..) I quite like him. and the storgest impression to me of Koenma was before he use the Mafukken (his pacifier) and prepare himself to block in the net with Sensui ... he looked very sad and serious which he has never show this kind of facial expression in the show but this time. He said this is part of his responsibility of letting Sensui torn and to besiege himself in the net with Sensui forever is his pay back ... very sad actually