The prologue and first mission in the Opera House already has several funny moments, but these can be summed up with "Dante just messes with Nero the entire fight and can No-Sell everything, even getting his own sword though his chest again".
As Dante tries to approach Kyrie, Nero makes a badass entrance by kicking Dante's face with his two boots. It's part-awesome, part-funny because the scene is briefly played in slow-motion and Dante barely reacts to it.
In the sword section tutorial battle after Sanctus's assassination, Nero revs his standard Order sword and asks Dante why he's packing a huge sword if he's not going to use it. Dante's response? Silently pulling out Rebellion, stabbing it in the ground, and fake revving the hilt like Nero just did.
When Nero has Dante on the ground and is repeatedly punching him in the face, it's obvious (if it wasn't already) that Dante has been holding back immensely. That said, he does seem to be getting a bit annoyed as his Devil Trigger flickers on a couple times before he decides to not just annihilate the poor kid with it. This choice leads to the Devil May Cry tradition of Dante being impaled by Rebellion at least once a game.
When Dante decides he's had enough and opts to run off for the time being once more guards are about to arrive, he leaps on out of there as Nero shoots at him — only to duck right back in with an adios and a cheeky little salute.
In the Special Edition, the opening cutscene for the Lady/Trish campaign starts off as a re-enactment and expansion of the regular story's midgame cutscene in Mission 12 wherein Dante, Lady and Trish are talking about the Order of the Sword. During the discussion, the girls are taking pizza slices out of the box, but Dante isn't exactly paying attention to this detail. When the girls leave the Devil May Cry shop, Dante tries to grab a slice of pizza without even looking at the table behind him, but it took him quite a while to realize that the pizza box is already empty.
Mission 2
Nero just casually ignores Berial's arrival from the Hellgate and slowly walks past him (Berial doesn't seem to notice him at all either). After a few steps, Nero sweeps up the dust and creates a dramatic wind to draw Berial's attention and curiosity. Then this exchange happens, proving that Nero isn't different to Dante when it comes to mocking demons before a fight.
Berial: When I came to this world 2000 years ago, there was no other human from the likes of you. Nero: Wanna make it another 2000? Berial: Silence!
Mission 3
Gloria defeating a small horde of demons by herself and sees a demon jumping toward her from behind, only for Nero to shoot it out of the air instead. While they are talking, Nero looks away embarrassed when he accidentally sees up Gloria's skirt.
Mission 6
Nero meeting Agnus for the first time in his laboratory after calling it a hellhole. Agnus yells at him to watch his words and the following dialogue ensues. Nero can be just as smartassed as Dante when he wants to be.
Agnus: Just as foul-mouthed as I had heard. The rumors prove true. As will the new ones concerning your d-d-d-demise. Nero: Don't you think that's a little harsh? Killing me because of the way I t-t-t-t-talk?
So Nero's walking through the forest one day, when suddenly...
Dante meets Gloria, there's a brief silence and some death glares between the two as Nero walks away in the background. What does Dante do next? Burst out laughing and saying that "that regal look suits [her]." This is because he knows she is Trish.
Mission 11
Even as he's being sucked into the Savior, Nero still has enough sass left in him to goad Dante to come get his sword back and to flip him off.
Dante: Heh... What a punk...
The Savior is revealed in full as Nero and Kyrie are absorbed inside it, it "powers up" and flies away, and it's a gigantic creature that would normally herald a Mass "Oh, Crap!" from the cast of any other game. Meanwhile, Credo is dying in the background. Here comes Dante whose only reaction to the Savior is an unimpressed "Check it out. It's got wings!" Then Trish agrees: "The design shows a terrible taste."
Mission 13
When Dante is taking on the She-Viper Echidna, she shoots her seed pods at him, and he kicks them right back at her. After they bounce off her head, we have this exchange which brings to mind Dante's memetic question from Mission 7:
Echidna: What the... [the last pod hits her, which leads to her saying in a supremely pissed off tone] Who the HELL are you?!
Mission 15
Dante faces Dagon. Unlike how Nero meets Bael's Rusalka "lures" for the first time (since they're the same kind), Dante is VERY happy to see Dagon's "lures" and even tries toflirt with them. But he manages to avoid Dagon's attack, thus leading to this conversation. The comment about the smell is made even funnier if you notice that, just before the battle, Dante plugs his nose.
Dagon: What? How did you know? Dante: You can hide your body, but that smell... Hoo! There's no covering that up. Dagon: Insult me one more time and I'll make you suffer more than you thought possible.
Dante then acquires Pandora after defeating Dagon. After it turns into a few different ranged weapons, it turns back into a briefcase and a bright light comes out... Dante closes the lid hastily, breathes a sigh of relief, and the floor just breaks.
Mission 16
In Mission 6, Nero is faced with a life-sized board game where he has to knock around an oversized dice to move a figure shaped like him across the board. Nero doesn't exactly react too strongly to that, but he surprisingly goes along with it without batting an eyelash. When Dante reaches the very same room in Mission 16, he casually and nonchalantly walks as the board game prepares itself to do the same thing for him, full with a Dante figure. Dante shows his utter lack of patience for that gimmicky bullshit and cuts down the dice, triggering a battle gauntlet instead.
The cutscene of Dante trying out the newly-acquired Lucifer. It's filled with innuendos, then it tips off at the end with Suck My Rose where the monolithic Hellgate forms a split-open heart-shaped rubble as Lucifer's blades explode.
Dante: First I whip it out! Then I thrust it with great force! It penetrates every angle! Until, with great strength, I ram it in! In the end, we are all satisfied.
Mission 17
Agnus and Dante wax Shakespearean in truly hammy style before their fight, complete with a fitting background music, dramatic lighting effects and confetti. What seemed like a gloomy and abandoned opera house at first became a stage when a Dramatic Spotlight suddenly shines on Agnus, then Dante decides to act appropriately to the location, complete with his own lines. It's mostly a reference to Shakespeare's Hamlet, as evidenced by Agnus holding a skull, and Dante's "And the rest...is silence.", but mixed with the over-the-top formula of Devil May Cry. In the Gallery menu, this cutscene is even hilariously titled "Agnus Redux".
Mission 18
In the opening cutscene, Dante tosses the sheathed Yamato around like a boomerang in order to hit the Angelos surrounding him. The Alto Angelo armor that Sanctus controls at that time anticipated the move and dodges the weapon by spreading its legs.
Mission 20 and Ending
As Nero and Kyrie slowly lean forward to kiss each other, Nero suddenly shoots the camera with his Blue Rose. It turns out their kiss was interrupted by Scarecrows suddenly appearing in front of the Opera House.
The Lady/Trish campaign of the Special Edition shows that Dante, Lady and Trish were still in front of the Opera House, watching Nero and Kyrie kiss off-screen. Among them, Lady has the most interesting reaction as she lowers her glasses just to watch what's going on. Trish also says this line which seemingly pokes fun at Dante not having a romantic partner.
Trish: At least someone knows how to get the girl.
Miscellaneous
To be frank, ANY battle that involves Dante fighting with the previous bosses that Nero didn't kill are epic.
The additional costumes introduced in Special Edition carry over to (most of) the cutscenes, which, depending on the scene, adds to the hilarity. Seeing Dante ham it up against Agnus or do a Double Entendre-laden dance routine is funny enough by itself, but seeing him in the Sparda outfit as he does makes it downright sidesplitting.
There's something darkly humorous about the fact that while Nero is having his entire world being turned upside down, unveiling the corruption of the island and his adoptive brother's involvement, questioning his own humanity and generally having an awful time, Dante is just goofing around, with the whole thing being compared to a holiday for him by the likes of the Gaming Brit.
of Dante trying out the newly-acquired Lucifer. It's filled with innuendos, then it tips off at the end with Suck My Rose where the monolithic Hellgate forms a split-open heart-shaped rubble as Lucifer's blades explode.Dante: First I whip it out! Then I thrust it with great force! It penetrates every angle! Until, with great strength, I ram it in! In the end, we are all satisfied.