Shirou beats the crap out of Guiche so thoroughly that he comes back to learn how to do that.
The entirety of Shirou vs Karin. Starting with Shirou surviving the equivalent of octagon class magic (which manages to break Rho Aias), then ending with a badass Crane Wing Three Realm.
A more subtle one, not related to combat. When Louise finally drags a confession out of Shirou that "Yes, he wants to save Tabitha", Shirou proceeds to pretty much single-handedly create a Black Ops program for Tristain, all in order to do so. The Smart Guy of the Undine Knights is thoroughly amazed by Shirou's ingenuity. This is a remarkable moment quite on par with Shirou in Heaven's Feel, when he decides he wants to protect Sakura rather than his lifelong ideal, and a crowner for the author for getting it right.
Throughout the entire story, Sheffield, a Servant bearing the Mind of God class, has been progressively built as the biggest threat to Shirou personally. Each time they clash, the battle scenes grow progressively more and more awesome until Chapter 22 wherein Sheffield realizes just how powerful Shirou is. According to the author's notes, this single scene had been planned from the very beginning of the fic, some 300,000 words back.
Shirou: All my life had been: Unlimited Blade Works.
And even with the above moment, Sheffield doesn't go down! Even better, after all of the impressive magic and tactics thrown around, he wins using the old "your shoelace is untied" trick!
