Shirou getting KO'd by Sylphid's weapon-grade Moe in chapter 8
A small part of me, the part that's usually reserved for desperate battles, after receiving grievous wounds, a part that's separate and capable of dispassionately tallying up the damage while the rest of the body was incapable of anything but writhing in pain, noted that I had lost the ability to form coherent words.
"Big brother? Are you okay? Kyuui!" Irukukuu leaned forward, one finger resting on the side of her cheek as she looked at me worriedly.
Hmm, that dispassionate side of me noticed I also seemed to have lost all motor functions. This could be bad.
Not to mention Irukukuu doing the same thing to a room full of people in Chapter 20.
The reactions of a horrified Louise and a drunken outraged Siesta at being told of Eleonore's reaction to...taking a liking towards Shirou.
Louise's face had begun to turn red as all the alcohol hit her slender frame at once. "But why!" she wailed, sounding bitter and confused. "Why was she saying Shirou's name?"
"Shirou is so strong and so manly, that even noble girls long to be brought over his knee and…" Siesta began, and then paused. "What!" she roared, slipping back into angry mode. "That bitch is after my man!"
Right in the midst of one of the stories most epic battles we get this gem.(covered by spoiler tag since its from one of the last few chapters.)
I began to laugh at her, slowly at first but gradually getting louder. It seemed to snap her out of whatever panic she had fallen into. "You," she hissed, her hands clenched into fists and her voice furious. "You think this is funny! You betrayed your Master too! You treacherous…"
"No!" I exclaimed, holding one of my hands up desperately. "No, not that. It's just, well, this entire battle, your boot has been unlaced."
"What?" she asked, confused by my observation, and glancing down involuntarily to see what I was talking about.
That was when I sucker punched her.
From the same final battle, after Shirou unveils Unlimited Blade Works
"I picked a fight with him," Guiche muttered, rocking back and forth. "I can't believe I picked a fight with him. What was I thinking, picking a fight with him? It must be my mother's fault. She must have dropped me on my head when I was a child…"
The beginning of chapter 15 starts with some pretty grim implications following the ending of the previous chapter, from Shiro raising an axe against the party that has wronged him, to Shiro saying how there would be no witnesses, and to Tiffania cries of desperation. It turns out, Shiro is just chopping wood.
Agnes' petty revenge against Shirou for when he used her as an example of women who would beat you up if you weren't nice in Chapter 15. Using a combination not-so-Accidental Innuendo, his Memetic Sex God reputation, Tiffania's *ahem* assets and her own sweaty appearance after training during Shirou's reunion with Louise and Siesta to get him beaten up? Priceless.
Shirou's realization of what Agnes has planned is also pretty funny.
"Oh, you bitch. You didn't."
Oh, and just after than, Siesta gets her revenge for being tricked by Agnes by switching her tea out for mud. Twice.
The Evil King Gilgamesh the Smelly. That is all.
"You just have women falling out of the sky for you! Why! Why can't they fall out of the sky for me!" Right then, in what I instantly knew as absolute proof in both the sentience of the Root, and that it was indeed a malicious entity that took joy from the pain of others, a naked woman fell out of the sky and landed feet first on the boy in the middle of the meltdown with a loud shout of "Kyui!" Truly, there could be no other reason for this to happen than irony being one of the driving forces of the universes, even more so then gravity or thermal dynamics.
The long set-up makes the line in Chapter 17 hysterical:
"You see, Master," I told her. "This is what happens when you start rumors about someone being some kind of sex god: people try to pray to them." The look on her face almost made the Root be damned rumors worth it.
Shirou having a psychotic breakdown and deciding to become an anti-hero by killing everyone in the world of Tristain, then waiting to be summoned in the Holy Grail War, using its power to force the Root of the World to become a human male form, and kick it in the balls so that the entire reality will feel it.
The old boys-peep-in-girl's-bath situation orchestrated by a group of would-be boy knights as part of a 'military training op', after which Shirou walks away to figure out what the operation was missing. Once out of sight, he Traces a couple of things.
Things like a four foot tall copper gong, and a six pound iron mallet.
"That's what this operation is missing," I said to myself in a cheerful tone. "Casualties."
The scene with Shirou and Siesta the first night he cooks at the Charming Faerie Inn while on campaign in Albion.
The running gag, started in Chapter 4, where Shirou insists on always pouring Derflinger a cup of tea.