Holly: Are you implying that I occasionally stray from the rulebook?
Foaly: I'm implying that you don't own a copy of the rulebook, and if you do, you've certainly never opened it.
Holly: ...Fair point.
At another point, Colfer has one of the best lampshades of the Idiot Ballever:
"Any first-day chemistry student could have told Ragby never to put sparks near a mystery gas. Unfortunately, Ragby had never met any first-day chemistry students, so it came as a complete surprise when the gas passed by Mulch Diggums ignited, in a chain of miniature explosions."
After spending the whole of the first novel always getting the last word in any banter, Holly finally beats him to the punch and all Artemis can come out with is "...I don't like lollipops..."
"Butler's eyebrows nearly jumped off his face. 'Santa Claus?'"
The Arctic Incident
When Butler goes against his training and makes as much noise as he can (he's making a diversion). His shame over performing a spinning kick is just icing on the cake.
A Mood Whiplash moment during The Arctic Incident: after inadvertently severing Holly's trigger finger and hastily managing to reattach it Artemis briefly lets his emotional guard down just in time for Holly to deck him hard enough to knock him into a nearby snowbank.
The Eternity Code
"This building has been hit by more lasers than the Millennium Falcon."
Mulch: You're right. I've got a smart mouth, and I deserve everything I've got coming to me. If it was me, I'd bury me alive. Chips: Bury you alive! That's terrible. You'd be screaming and clawing the dirt. I could get nightmares. Mulch: I promise to lie still. Anyway, I deserve it. I did call you a pair of overdeveloped, single-cell Cro-Magnons. Chips: Did you? Muclh: Well, I have now. Pex: Okay, Mr. Digence. You know what we're gonna go? We're gonna bury you alive! Mulch: Oh, the horror! Pex: You asked for it! Mulch: I did, didn't I? Pex: Nobody calls me an overdeveloped signal-bell crow magnet! Mulch: No, I bet nobody does... (later, after they've done the deed) Chips: That was horrible. Horrible! The poor little guy... Pex: Yeah, well, he asked for it. Calling us... all those things. Chips: But—buried alive! That's like in that horror movie. Y'know—the one with all the horror. Pex: I think I saw that one. With all the words going up on the screen at the end? Chips: Yeah, that was it. Tell you the truth, those words kinda ruined it for me. Pex: Don't worry, buddy. There are no words in this movie. Chips: Y'know, it's much more real than a movie when it's real. Pex: It's the smell. You can't smell stuff in a movie. Chips: Digence must been upset right there at the end. Pex: I'm not surprised. Chips: 'Cause I could see him cryin'. His shoulders were shaking, like he was laughing. But he must have been crying. I mean, what sort of crazy wacko would laugh when he's gettin' buried alive? Pex: He musta been crying. Chips: Yeah. He musta been crying. The very next line of text: Mulch was laughing so hard he nearly choked on the first shovelful of dirt.
Jon Spiro in his inner monologue missing the days before employment regulations:
The Big Bad has his consciousness placed in a guinea pig's body. His guards enjoy throwing him weapons that he's too weak to pick up.
The Time Paradox
"Quantum zombies. I'd like to get a copy of that program."
"Peace be inside me, tolerance around me, forgiveness in my path. Now, Mervall, show me where the filthy human is so I may feed him his organs."
Then there is this gem concerning the Kraken from the Time Paradox:
Holly: So... you're saying that Shelly is going to light a fart?
Foaly: No, I'm saying that Shelly is going to light THE fart!
Foaly then goes on to say that the last time this much bodily gas was in one location was at the last dwarf tribal gathering.
"It's not a lemur, it's a monkey!"
Artemis winks at Holly to communicate that he has everything under control during a tense situation.
At least Artemis hoped this was what his wink communicated and not something like 'Any chance of another kiss later?'
In book 6, when Holly realizes Mulch stole her omnitool years ago and he tries to wriggle out of it before admitting to it and coming up with a Freudian Excuse.
"Where did you get this?" she shouted. "How did you get it?" "A present," offered Mulch lamely. "From my... eh..." He squinted to read the writing on the base. "From my mother. She always called me Holly, because of my, erm, prickly personality." Holly was angrier than Artemis had ever seen her. "Tell me, Diggums. The truth!" Mulch thought about fighting. It was in the curve of his fingers and the baring of his teeth, but the moment passed quickly and the dwarf's natural passive nature surfaced. "I stole all this stuff from Tara," he admitted. "I'm a thief, aren't I? But, in my defence, I had a difficult childhood, which led to low self-esteem, which I projected on to others, and punished them by stealing their possessions. So, in a very real way, I am the victim here. And I forgive me."
Trouble Kelp:Sir now, is it? Your exact words were, and I quote — obviously, since they are your exact words — you said that Artemis Fowl was "crazier than a salt-water-drinking troll with ringworm." Holly: That was earlier. I have shot Artemis twice since then, and he's fine now.
The Last Guardian
The entire conversation between Gobdaw (possessing Myles' body) and Artemis in The Last Guardian. Artemis essentially trolls Gobdaw into revealing himself after pretending his spirit had left Myles' body.
When the narration describes the Silver Cupid, a shuttle customized by Foaly to accommodate Artemis and Butler. Regarding the vehicle's name, it mentions:
It was a little romantic-sounding for Artemiss taste, and so Holly referred to it by name as often as possible.
This bit from early in The Last Guardian:
"Hey," snapped Holly. "This is not the time to blame Artemis."
"Thank you," said Artemis. "Finally."
"There will be plenty of time to blame Artemis later, when this is resolved."
Especially funny because, for once, Artemis has done nothing wrong and is not even slightly at fault for the current situation.
"I am Butler. Everything I say sounds tough. Now, get out of the lake, fairy."
In a short story, Holly is undergoing the LEP recruitment trial, and she has to either avoid Commander Root for a full 24 hours, or else shoot him (with a paintball gun) before he shoots her. Unfortunately, while she's being hunted, there's a fiasco involving Turnball Root, and the mission goes sideways. Holly only saves the day by being her usual Cowboy Cop self, earning herself a chewing out from the commander. At the end, Root gives her one final chance to convince him not to flunk her. She pulls out her paintball gun and shoots him in the chest.
In a short story, Holly (pre-LEP) is wearing a traffic vest which shows her vocal commands. Unfortunately, she runs into a wave of gel, which shorts out the suit. Her last word, just before the gel hit, was "D'Arvit." And then she gets summoned to meet with Commander Root. Just imagine going to a job interview with a swear word written on your chest.
Myles and Beckett's reactions to Artemis putting a combination lock on his lab door - Myles works out the combination after three days of work and several rolls of toilet paper, and Beckett digs a bear trap for Myles and gives him the ladder in exchange for the code.
Trouble, knowing Holly's nature, gives her a direct order to stay where she is and do nothing, not to investigate the current mystery, and most especially not to do so with the criminal Artemis Fowl. Artemis wonders whether he even expects this order to be obeyed, before Holly explains that he's just covering his bases with his superiors.
Mulch Diggums manages to get in a some decent ones in his interactions with Commander Root:
Saying that he doesn't know her first name and guessing that it's "Britney."
Telling her that she's like David Bowie if David Bowie were a fairy, so essentially, she's David Bowie. Then asking if humans will ever figure out that he was one of them.
Claiming that he's not simply a criminal but an artist, all while picking her pocket.