What impressed me is the ability of this obviously nuts person to do serious roles such as in Good Will Hunting and The Fisher King. Of course, him having DJ'd with jokes for free for the soldiers during the Gulf War kind of earned him a place in my heart.
As for the others, you probably know Weaving as Agent Smith in the Matrix movies, and Stamp as Supreme Chancellor Valorum in Star Wars Episode I.
Actually, Terrance Stamp is better known as General Zod from Superman II.