The Berserker: Kiri replaces Lancelot as the Berserker class in the 4th Holy Grail War.
Heroic B.S.O.D.: Kiri, when he finally return to the Throne of Heroes after his participation in an alternate 5th Holy Grail War.
It Can Think: One of Berserker's defining traits - while still a berserk warrior, he can strategize and will pull back when needed. The fact that he can use magic also lends credence to this.
Oh, Crap!: Everyone has this reaction when they learn that one of Berserker's Class skills is A-RANK INDEPEDENT ACTION, as it means that he is essentially an monster that can only be controlled by command seals and killing his master won't immediately stop him.
Trauma Button: Downplayed, but Saber has this reaction when Iri makes a comment about dressing her up (it's a joke), as it made her remember all of times the clan forcibly dressed her up in several (at times rather embarrassing) different outfits.