The sheer dissonance one can get from customizing win images and taunts. So you can get things like a winning image of Shigechi grinning happily while the text box has him ominously state he has a bad feeling, or an image of Will A. Zeppeli sneezing while offering to tell his opponent about his life story.
For Rohan: Taunt B (Holds pens in front of his face, looking amazed) + "Let's see how this tastes." = Rohan the Extreme Omnivore. Just As Disturbing In Context, since that quote is originally associated with a pose that has him point at his opponent.
And a similar situation for Gappy: Apply his Taunt B vocal ("Delicious!") to his Taunt A animation (pointing fiercely at his enemy.) Cue Gappy pointing at them and shouting "DELICIOUS!" while grinning.
And a similar note for Kars: Equip his Taunt A animation with his Taunt D vocal ("Ha ha ha ha ha! You've certainly got guts!") and watch his mouth go from grinning and laughing to dropping his smile in an instant. How very Ha Ha Ha No. Heck, that line gives a Ha Ha Ha No vibe with every pose except its default, and even then, if you perform it with Ultimate Kars, his mouth actually animates now only to go through the same Ha Ha Ha No motions.
Another, this time for Fugo. Heartfelt voiceover and winquote congratulating his opponent for their efforts, accompanied by a win screen of an enraged Fugo shaking his fist at them and screaming at them.
Zeppeli victory pose C (spitting out Hamon wine projectiles) + "Ah-choo!" = Sneezing wine projectiles.
Zeppeli taunt pose B (holding his arms out in a Bring It pose) + "You wouldn't happen to have a corkscrew, would ya?" = Mundane Made Awesome.
Baoh's expression rarely changes, which makes for some pretty amusing situations where other characters look like they're freaking out, such as when hit by Giorno's slow-mo punch, or when subjected to some Dramatic Finishes (particularly Philadelphia Coastline's).
William A. Zeppeli's backwards walking animation. There are no words for how goofy it looks and sounds.
One of the English localisation's rather naughty-sounding lines in story mode for Part 1:
Zeppeli drives his fist deep into Dio, hoping to blast his Hamon energy into him.
Zeppeli's Taunt D quote 2:
Zeppeli: I love the sound of Overdrive in the morning!
Joseph's counter taunt special. He says "Your next sentence is: <opponent's taunt>". Then the opponent is forced to taunt and his/her "taunting panel" appears, then they realize what Joseph did and their "taunting panel" is changed to their "being taunted panel".
Even funnier is how he literally imitates Part 3 DIO's "WRYYYYYYYYYYYYYYYY!" and Valentine's "DOJYAAA~N!"
Made even more funny how he imitates the way Iggy chews his gum. And that the narrator has to helpfully point out that Iggy is shocked.
Best of all is how he imitates Baoh's "BARUBARUBARUBARUBARUBARU!", and Baoh being shocked at Joseph's correct guess... despite the fact that Baoh cannot say anything else in his battle form.
...and as such, the narrator must convey Baoh's shock for us, as opposed to Baoh gasping in surprise like the other characters.
Speaking of Joseph, the Western release of the game does a good job of finding a way to deal with his old "Happy, joy-py, nice to meet you-py!" taunt line, by changing it to a cute little Spoonerism instead: "Damn meased to pleet ya!"
His counter where he starts crying. Silently when the command is input, then when hit he lets out a "HEEEEEEY!" and then whines that "IT'S NOT FAIR!". The opponent gets so shocked he gets a huge drop to his HH Gauge.
Jean Pierre Polnareff was localized as... Jean Pierre Eiffel. His name is still a musical reference, although the band he's now referencing, Eiffel 65, wouldn't be formed until eight years after his first manga appearance.
Polnareff's bewildered reaction to each of Passione (Part 5 protagonists, sans Fugo) greeting him like they know him following by an insistence he doesn't know who they are.
Part 3 Joseph's Gratuitous English taunts: "OH MY GOD!", "HOLY SHIT!", and "SON OF A BITCH!" Made all the more amusing in the Japanese version when they're all spelled out in capital English letters.
Remember Part 2 Joseph's special ability to sprint in the opposite direction of his opponent? Part 3 Joseph sure does, and still puts that legwork to good use.
His GHA. Josuke heals his opponent to full health, then batters them so badly, they're worse off than before. Especially in the case of Johnny. Josuke's heal allows him to stand again, but the ensuing beatdown cripples him once more. Looks like the only thing worse than insulting Josuke's hair is mockingly complimenting it. Here's the link.
Valentine: The first thing I'm going to do in office is outlaw that ridiculous hairstyle!
Baoh: Since Ikuro/Baoh can't talk properly, the narrator speaks for him, claiming that Baoh doesn't like how Josuke's pompadour smells. Yet Josuke still figures it out, gets pissed off, and takes it out on poor Ikuro.
Narrator: Baoh has detected the scent of his foe's hairstyle... And he doesn't like it one bit!
The last part of Okuyasu's Great Heat Attack. After a painful beatdown with The Hand, Okuyasu gives his opponent a badass glare and a smirk... then a flowerpot comes out of nowhere and whacks him in the face.
Now, we all know that most of the Stands in the game had to be renamed for the English version because copyright law in Japan is radically different than the rest of the world. But Part 5 got hit particularly bad. Sticky Fingers, just to name one, is now Zipper Man. And the best part is that this was apparently Araki's idea.
In the Western localization, Jolyne's Heart Heat Attack quote is changed from "How many throws (of the ball) can I do in a row? A thousand!" to "How deep can I hit? Balls deep!"
The fact that Johnny can still say his "I don't feel like dismounting today." taunt when he's not even on his horse.
The mostly serious Valentine prefacing his HHA with his comically adorable "DOJYAAA~N" line and a shrug.
Valentine's GHA is localized from "Dirty Deeds Done Dirt Cheap" to "Filthy Acts, at a Reasonable Price."
To add to that, it's clear the localisation team was frustrated about not being able to use the original full name or were knowingly teasing fans who did know the full name, by translating Valentine's generic opening line to "Time to perform some nasty acts at a fair and reasonable price!" Even better is this borderline Mori-esque line in the Jojo Glossary page for D 4 C:
No one knows what this mysterious abbreviation means.
The best part is that, since the game's soundtrack was untouched, you can hear Valentine say "Dirty deeds done dirt cheap". In English.
The fact that, in the game's exclusive story, Jonathan reacts to Jo2uke's perfectly normal question of "Who are you?" with "I don't give my name to scum like you!!" Geez, the hell's your damage, Jonathan? (In the Japanese version, he mistakes him for one of Dio's zombies, a detail the localisation missed out.) In fact, there's something hilarious about every protagonist going hostile on poor Gappy at first sight, but Jonathan's uncharacteristically brutish response is probably the funniest.
The tense and threatening "Eccentric Blaze King Esidisi" (the named character's theme) is mostly synthesizer, except for the one guitar part in the center. And what's the guitar playing? "Back in Black", of course!
Stephen Steel is the "host" for the Campaign mode. Choose to leave it and he goes a little... overboard.