Gilgamesh

[ the fact that Kirei had taken on another Servant was almost insulting, if only for the fact that it brought his loyalties into light. Gilgamesh would not have minded a lowly mongrel like Lancer, but instead he had found himself in the company of another who would claim kingship -- one who claimed kingship over him -- and suffice to say, he was less than pleased.

far be it from him to whine to Kirei like a petulant child, so he dealt with his ire in other ways.

namely... smiling at Rider whenever he was granted the opportunity, not unlike a master smiling at his adorable, stupid puppy. ]