Flag 128, when Keima is writing Shiori's story with her (in which his character, Cashiragi, gets killed off as a result of Shiori's anger with him), and she forces Cashiragi to get eaten whole by a wild Rembatos Beast. The rest of the story?
Keima: "Cashiragi wasn't digested and escaped from the poop! Truly, it was a miracle!"
Keima is able to delay Luna/Vulcan just by reminding her to clean up the library!
Shiori catching Keima wearing a girl's uniform and gloating about being the 'God of getting captured' as part of his re-capture of Yui in chapter 141.
After wrapping things up with Yui and Mars, Keima tells Haqua that they still need to keep their guard up. Immediately after saying that, he walks into a giant fish that tries to eat his head.
The little argument in 158 between Vulcan, Diana, Minerva, and Mars over who Keima belongs to. He was not amused, but the readers and Elsie were.
The first few pages of chapter 168 are an hilarious exchange between Keima, Diana and Tenri while Keima's in the bath.
In the same chapter, the magic ear. It just comes out of nowhere.
The side-story "Once Upon A Time In Maijima" is a slapstick western with Shiori as the heroine, Kodama as the villain, and all the other capture targets as various characters in the town. So what role did Keima play? He's Shiori's horse.note It's a pun on his name, which translates into "cassia horse".
As if chapter 179 weren't amusing enough due to Keima's secret weapon for capturing Ayumi (her panties), it's made absolutely hilarious because due to Vintage targeting all of his previous conquests, Chihiro is dragged along for the ride the whole time, with absolutely no idea what's going on.
The ending, where Haqua tells Chihiro that Keima is fighting to protect them all. A seemingly serious scene... whose mood gets killed quickly due to said line being said followed by a full body shot of him holding Ayumi's panties.
The entirety of Flag 183. Ayumi thinks escalating things will make Keima give up. It doesn't work. She demands he marry her to prove his love. He accepts. She takes him to meet her parents (note that this is almost the middle of the night), and he tells them he took their daughter's first time. While fleeing Ayumi's raging father, he drags Ayumi up to the roof, pulls out a wedding dress, and officially proposes.
In Flag 190, the goddesses' conversation on: Keima, who gets him, and the appeal of their hosts.
Mars stating how far she thinks her host would go.
Mars: "Yui is the sort of girl who'll convey her feelings even if she has to rape him." Minerva: "Uh, Um, Shiori too..." Vulcan: "H-Hey, you girls..."
Continuing the conversation,
Apollo: "Minerva can't kidnap a man yet!! (flips Minerva's shirt-skirt to see underneath) Not with this." Mars: "Though there are some men who like that. Maybe Keima's one of those."
In Flag 193, one of the "alternate worlds" Keima enters is one where Maijima High School is an all-boys school and the Weiss are hiding in boys, and well... Keima is told he still has to get them out with love. Or rather, he is told to continue doing it, which is even funnier.
The first "alternate world" he visited is actually even better than that: It's a world where Keima basically made a No Damage Run of the Goddess arc, resulting in all hosts being head-over-heels in love with him, seem to barely mind having to share, and appear to try to out do each other in who can express her love for him more through cooking. For reference, Ayumi meets him at the gates calling him "darling!" and herself his wife with a bento in hand, Yui appears dressed like a knight in a chariot pulled by her butler, with a bento of her own and listing all the things that'd make her a great wife before declaring she'll marry Keima as well, with a marriage dress ready for Keima, Tsukiyoslam dunks him with a tea tray and declares they'll have tea at the roof, Shiori is spotted reading as much material as she can find on cooking, and Kanon has a whole frickin' blimp floating above the school "advertising" treats "for the one you love!" Even in the middle of a minorLover Tug-of-War, Elsie of all people is the one to lampshade the situation.
Elsie: "Wooow, it's just like the games Nii-sama plays!"
Even better, one of the worlds is the 2D world with Yokkykun! Then Keima is woken up and reacts just like you expect. At the end, Keima, sick of this, wants to go back to his world. But then he changes his mind and wants to go back to the game world.
Much of chapter 202, due to Keima's out of character antics to try and give Dokuro a sense of familial closeness (while his mom comments on it), and Dokuro's childlike naivete. But what really takes the cake is Elsie's reactions to Keima acting like a big brother to Dokuro as well as being left out.
Keima: "Things will get complicated if mom meets you! We don't have any more open spots in our family!" (Cue Elsie sitting in a box with the note 'Please take care of this cat'◊ on it)
In chapter 206, after a few already funny moments of Keima chasing after a Red Herring (Urara's porn magazine which she kind of stole from her grandfather's room), Urara's invitation for a "porno mag enjoyment party". Keima's (only in thoughts) response sums it up best.
Keima: "What the heck?!"
One chapter later, after he was forced to read the magazine with her (because he could not allow himself to refuse lest her capture points drop), she started making childlike advances on him and eventually got to forcefully undressing him. Keima was very much not amused. Made even funnier by the fact that there were other kids watching, and Urara was not aware of it.
The next chapter Keima is overpowered by Urara and teased by her.
Chapter 216 has Keima's plan to conquer Urara, which is staging a spaceship crash, playing the role of an alien. It works...but Keima sure as hell didn't count on Urara bringing Mio and Yui to help him out. Keima's face says it best.
The next chapter has the 7 year-old Urara, Mio, and Yui's attempts to help the alien Kei(Keima). They nearly drowned him trying to hide him, then, while he was unconscious, they stripped him naked to dry him off.
In chapter 220, Yui is babysitting a 7 year old Keima who's currently stuck in Keima's current 17 year old body. Yui plans to make Keima fall in love with her by winning over his younger self with games; once the original Keima returns, he will fall for Yui since she reminds him of the girl who treated him with games. The plan works... except young Keima doesn't realize the crossdressing Yui is actually a girl. Cue this hilarious line:
What makes it more funny is the fact prior to said line, Yui was trying to keep the guards away from Keima, and Shiori and Tsukiyo were just outside the Goidou household during the whole thing, with no idea on what was going on.
In episode 2 of season 1, the morning after Keima reluctantly accepts Elsee as a younger sister, they are shown in class. While Keima contemplates how many more loose souls he has to catch, Elsee passes a note for him to Chihiro, who was asked to read a passage from their current lesson. Chihiro then reads Elsee's letter, much to the latter's and Keima's embarrassment, putting emphasis to the incident that happened in the bath. What's funnier is that some of Keima's male classmates (super deformed) stacked themselves in a pyramid while repeatedly asking "What happened in the bath?" in chorus.
Episode 3 focuses on Mio's capture which Keima initiates by being her chauffeur, using a bicycle. Whem Mio refuses, Elsee uses her magic robe to add a carriage to Keima's bike. As the days progress, the carriage becomes larger and more elaborate, two carriages being a Zaku head and an interstellar locomotive, and at that point Keima gives up.
The final episode of the anime's first season. How can Keima's 'Capturing God' moment be made funnier? By making that scene a Theme Music Power-Up.
And then he's off to frolic with girls, singing hilariously off-key.
The final episode of the anime's second season. War of Keima clones is even funnier. And then they turn into adorable midgets.