Illya's Imagine Spot when she see herself as a mafia princess when she thinks Shirou will resurect a mafioso/yakuza to solve their problems. What sold it is her asking if she can tan her bodyguard and call him Berserker.
Chapter 9: Illya in general, when she isn't being awesome.
Illya: Heeeyyyy onii-chan, come on and have a look at this. I've got minions.
Later, she considers promoting one of them. The levels of advancement are (from lowest to highest): minion, lackey, flunky, crony, pawn, and servant.
Illya: Once they've reached the rank of servant then we can give them official badges."
Shirou sends a minor curse of misfortune on someone stalking Illya, assuming it was an agent for the resident Mages Association or Godou. It actually was Sorimachi, a huuuuge otaku obsessed by little sisters-dating sims who thought Illya was the "perfect" little sister... only to learn she already had a big brother.
Several months later, the curse is STILL active.
The Eighth Campione, a Supreme Ruler towering over any absolute monarch, is reduced to grovel and beg his new housekeeper to not keep him away from cooking duty. Even Shirou later acknowledges it's Actually Pretty Funny in a poetic way.
To add insult to injury, Asuka-san manages to cook better than Shirou. Cue decision to shamelessly ask for lessons.
Godou somehow partially dematerializes a Noble Phantasm. They're not supposed to be able to do that. Keep in mind, Nasuverse magic is really glitchy. There are more exceptions than actual rules on the high-end of thaumaturgy, but we have never seen someone break the rules of magic... through sheer failure.
Shirou: By the Root! Had one of the gods Kusanagi slew been a deity of manhood and fertility?!
It's even more amusing when one remembers that it's Shirou who has such an authority.
Guinivere trying, and failing, to stop her growing attraction to Shirou.
Illya meeting Liliana while out shopping and asking about how things are going. It's just the usual fare, Lily blushes when said to be part of Godou's harem. But then Illya asks her about "the situation between her onii-chan and Godou", and then ever so slightly backs away at Lily'sreaction.
People wondering what the hell Shirou was thinking when he made the Feast of the Kings and later on inviting Guinivere, the Queen of the Divine Ancestors to attend. Jump Cut to Shirou thinking what the hell was he thinking at the moment.
The entirety of what one of Shirou's authorities, namely Hero's Bride, does. Or rather, who it targets, because over time it manages to become increasingly amusing and absurd. So far the targets are his homunculus younger sister Ilya (with her "I can't really be with him because we're siblings and it's sad" thing) who once tried to kill him, divine ancestor Guinevere (whose precocious-seeming crush is fairly cute) who should by all means be his enemy, and then fallen goddess Tiamat (who immediately started fighting with the former over Shirou) who actually was his enemy. As absurd as Godou's harem gathering is, the guy at least has humans in it, whereas Shirou goes for anything but. But then again, you'd expect nothing less from the guy who already wooed a Servant (Actually two) and the human vessel of the tainted Holy Grail.
Taken Up to Eleven in an omake where Hero's Bride becomes an Evolving Authority, getting more powerful with each God he slays. It Gender Flips everyone he saves to girls and allows him to make perfectly identical clones of them that can remain permanent. He has far more resources and power than he did even in the fic, but he feels he's honestly Blessed with Suck.
Athena bids Godou good morning by casually swinging her scythe at him. He casually blocks it and says, "Good morning" to her too. After a moment, it sinks in and he laments that he's starting to get used to the craziness.
Odysseus looks at a modern yacht and says it looks lame compared to his old ship. Then he admits that modern ships at least have bathrooms, and if his old ship had one, it would have made his voyages a lot more pleasant. Circe is disgusted and says he didn't have to mention that last part.
After being introduced to it, Lancelot quickly becomes an anime nut.
Erica suggests Godou try to seduce Athena and add her to the harem. He's incredibly shocked when the rest of his harem agrees and wonders why he's the only one who sees how crazy this is.
Shirou and Godou both accusing the other of having a harem and both denying it.
Shirou's inability to understand just how rich he actually is and having to explain to Illya with teddie bears just how much money something costs.
Rin learning about Rule of the Underworld. What make it worse is that Shirou actually had a nightmare about her finding out and still wrote about it his diary, a diary that he intended to send Sakura, you know, Rin's sister.
One of the other students at the clock tower is severely creeped out by the evil laughter she hears Rin make.
Her later daydream about making a ruby as big as her head in a Mystic Code. In front of Luvia Edelfelt, no less - serve this cow right, flaunting her wealth in front of our favorite tsundere!
Godou being chosen as the 'victim' of his class haunted house, just because his male classmates wanted to (fake) stab him.
The omakes where Kayneth summon Luo Hao as Lancer. There is something utterly catartic in Luo Hao sending Kayneth flying for being a rude 'vassal'.