Hirano: (switches to warm smile and bubble background) "Pretty please with sugar on top...?"
Saya: (sighing) "...alright."
When Takashi rescues Alice, and ends up stranded on top of a wall, surrounded by "them", it seems that things can't possibly get worse, right? Wrong. Four little words, perfectly understandable given the situation, make things worse, and yet also hilarious: "I need to pee."
In Chapter 22, Takashi and Kohta hid their weapons in the womens' lingerie department of the mall, underneath a pile of bras. Each gives the other credit for the idea while Kohta wears a bra on his head. Rei takes this opportunity to take a good-natured dig at Shizuka, saying "Only someone with TITANIC BREASTS would have any reason to look in there", while Alice exclaims with waving flags "Hooray For Perversion!"
The "Cosplay of the Dead" subchapter also qualifies, especially for Alice's choice of costume.
Also, the little "oh YEAH" sound effect when Shizuka appears stark naked except for a medicine bag in front of Hirano in Episode 7.
The Nietzsche Wannabe mall survivor's attempt to "go out like a badass", which involved flailing around a knife that failed to scratch a single zombie.
Alice and Shizuka using a flashlight to scare Hirano. Except Shizuka aimed the flashlight at her breasts instead of her face.
The extra chapter, a flashback of Takashi, Morita, and Imamura who got eaten in the first chapter talking about the girls in the school. At the end, it shows a now undead Morita with a zombie girl, still clutching his guitar.
The English dub has its moments.
Takashi: [after finding Rika's weapons cache] So she (Shizuka) lives here with a friend of hers, isn't that right? Who is she, Sarah fucking Palin?
The ending of the OVA where Takashi somehow manages to keep four scantily clad female zombies at bay while still under the influence of the funky smoke. How he avoided getting bitten through the night is anyone's guess.
Takashi slaps Saya to get her off him! Then right as she looks like she's gonna flip out...
Kohta hallucinating some sexual fantasies whilst going at it with a broom.
Some of the Woolseyisms in Episode 6's English dub are hilarious.
Kohta: [dazed and dumbstruck] I like turtles...
Takashi: [seeing Saeko wearing a Naked Apron] Man, I love girls' apartments. Everything's so stacked... uh, stocked, I MEAN STOCKED!
Saeko: Until I finish doing laundry, I'm wearing this, but I guess it's a little too revealing. Takashi: No, it's OK, I hadn't noticed a titty... A THING! We should be prepared, they could come atit- ATTACK!
At the beginning of Episode 10, Shizuka is rubbing medicine on Rei's back. After she leaves, Rei implies she wanted Takashi to be the one to do it, but obviously she doesn't tell him that. So she just points out that it's his fault in the first place.
Rei: My boobs are killing me because you used them to BALANCE AN AK-47!