Foe Yay Shipping: Izumi and Amagiya, who fight in a way that involves a fair amount of Clothing Damage, with Amagiya never quite letting go of his grudge towards Izumi for most of the series and Izumi intending to reunite with Amagiya in the afterlife. If the (limited) amount of fanworks is any indication, they're the most popular ship among the fandom.
Hilarious in Hindsight: Takeru and Fujimaru basically predicting one of the main spoilers of the series: that Kuroyuki is immortal, making their nickname of "old hag" for her surprisingly accurate. While Fujimaru may have known, there's no way Takeru could've.
Fujimaru is initially one of these, before dropping the Jerkass part and moving into general Woobie territory. Eventually, he graduates into an Iron Woobie.
Amagiya towards the end of the series, as his backstory is revealed.
Magnificent Bitch: Kuroyuki is utterly despicable, but you have to give kudos to her for being composed and competent through it all.
Moe: Shirayuki is generally agreed to be the cutest thing ever.
Moral Event Horizon: You could argue when exactly Kuroyuki crossed this, but she definitely has at some point.
Chronologically, experimenting on her own daughter pre-series is this.
In terms of the present, however, her telling Takeru to roll over and give up makes it clear that she knows that she's no saviour. It's also the moment where Takeru decides that she has to be taken down, and his will never wavers from there.
No Yay: Kuroyuki and Uzuki, once it's revealed that Uzuki is effectively Brainwashed and would not have served Kuroyuki otherwise, turning their sexual relationship into abuse/rape on Kuroyuki's part.