These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The Kashoyo. Zombie fairies (and not the cherub kind) who can survive being torn limb from limb, even going as far as reforming into regular zombies. All while smelling horrible and making a ghastly chittering noise.
Flandre, in her first appearance.
Purity Sue: The author is an open Yuyuko fanboy. Let's just say it shows.
Squick: Reimu's initial reaction to finding giant naked and anatomically correct statues of Sakuya and Flandre in Remilia's mind, until she realizes that there's nothing sexual intended by it. Also, everyone's reaction to the Kashoyo.
A far more serious example, the room where Sakuya prepares Flandre's meals.