Gaines blackmails Jack into putting an earpiece on:
Gaines: Now say something.
Jack: If you hurt my daughter, I will kill you.
Gaines: Good, that's a nice clear signal.
This scene is legendary. Jack and George Mason are, quite literally, out in the field. Jack, with Mason behind him, dramatically climbs and leaps over a fence. Mason slowly walks forward and nudges the fence slightly, allowing him to smoothly step past it. The look Mason gives Jack afterwards is absolutely priceless.
Jack needs to get access to a criminal organization's inner circle quickly, and the only way he can think of is to bring them one of their enemies. His superiors reluctantly give him access to one of the worst criminals they have access to — only for Jack to shoot him dead the minute he sees him, as there is no time to convince the criminal to play along, and Jack believes there is a quicker way to gain the organization's trust:
Nina: He is gonna put a bullet in my head before I can say hello and then he's gonna turn the gun on himself.
Jack: We'll make sure he doesn't turn the gun on himself.
At the end of the season, after spending the whole day pissing on everyone's chips, outright supporting the warmongering in Washington, arresting Tony and Michelle, and generally being an arse, Ryan Chappelle is sitting at Tony's desk after Jack, Tony, and Michelle's efforts have saved the day:
Chappelle: Tony, that was District Director Vaughn. He's so happy with what we did here today, he doesn't know where to start.
Tony: That's great.
Chappelle: So... what's up, my friend?
Tony: Well, uhh... it's like this. Either fire me, or get out of my chair.
In the first episode, Adam believes that Kim shouldn't be working in CTU and thinks she's only there because of her father. Kim's response to this is nonchalantly locking him out of the system, and she only lets him in again once he takes back his words.
Episode 14: Pretty much the entirety of Tony's interaction with Nina in the interrogation room, starting with Nina's attempted Hannibal Lecture, climaxing at the revelation that her pulse notably spiked when Tony told her that the medical records of the man they were looking for, who she had claimed she'd never actually met in person, showed that he had been treated for HIV, and ending with her calmly answering one of Tony's questions by informing him that his neck has started bleeding again.
Episode 23: Sherry getting punched in the face. Not quite as funny as Mandy, but she sure had it coming for a long time.
Jack and Audrey have to lay low for awhile at Tony's place, and they can't have anyone who knows that they're there leave the house, so Tony's new girlfriend gets detained when she has to go to work. Jack's usual methods of dealing with people aren't working so well, so Audrey tries to talk things out, girl to girl.
Audrey: Your boss will have to understand.
Jen: And what if he doesn't?
Audrey: I could have him killed.
In turn, there's Jack's deadpan reaction to meeting Jen after she yells at him.
Chloe: (takes off the device meant to check her blood pressure, frustrated) Look I'm fine, I'm the one who did the shooting.
Chloe offers to talk with Jack about anything he needs to. Jack reacts with a look of pure horror. Chole's face after he leaves is all, "Well, that went well."
In Episode 18, CTU apprehends a suspect connected with the terrorist plot. The terrorists find out about this and call "Amnesty Global" to delay the interrogation. Jack Bauer's reaction when he finds out from his boss, Bill Buchanan, about all this is priceless. Especially Buchanan's response to Bauer storming away.
Buchanan: Ah, Jack! Don't make it worse!
At the end of the episode, Jack interrogates the suspect with his usual methods. Afterwards, he calmly says "This'll help you with the pain..." and knocks him unconscious.
Episode 23: Mandy getting punched in the face. It's a combination of the framing of the shot (namely the entering of Curtis Manning's fist) and Mia Kirshner's facial expression.
Shari suspecting Buchanan of inappropriate conduct:
"Did you see the way his hand brushed against my shoulder as he walked away? That's wrong. He shouldn't have done that."
Mr. Landes: This is a dangerous situation. Tempers are high. So everybody just breathe.
Chloe: What is with you and breathing? Is that your solution for everything?
Chloe: This Lynn McGill person is really slowing things down.
Spenser: Yeah, that's his style. I worked with him once before. He usually loses about 20% of his staff in the first couple of days after taking control of a new office.
Chloe: That many people quit?
Spenser: No, most of them were fired.
The dialogue between Karen Hayes and Tom Lennox after she notices the bruise on his head.
Karen: Did someone push you down the stairs?
Tom: No, Karen, I tripped over your ineptitude.
Possibly the best part of Season 6 are all the awkward, disbelieving, if-you-weren't-my-boss-I-would-be-facepalming-so-hard facial expressions Tom Lennox makes in regard to Vice President Daniels' affair with his assistant. Then Tom is required to spend the next 40 minutes having to watch Lisa get it on with her other lover.
Tom Lennox: And... finally, we're done.
Hour 20: Tony Almeida is double-crossed by the person he hired to collect one of the weapons used by the terrorists. The double-crosser is overpowered and dragged to the bathroom for interrogation, where he expires between scenes, with his head propped against the side of a bathtub. In the next scene, the interrogator is seen coming out of the bathroom, freshly showered — with the body still in the same position as before, evidently forgotten by the people in the room.
Marika and her sister Rosa are having a heated argument about Marika's boyfriend Samuel. Then Jack and Renee smash their way in with guns. The look of astonishment on the girls' faces is priceless.
The First Gentleman, Henry Taylor, gets drugged and can't speak properly:
"You killed my son, you killed Rrroger!"
Episode 11: Jack is in the middle of interrogating a government official who's working for the terrorists, when the president calls and, despite his efforts to justify his actions, she orders him to stand down. Jack's responds by tasering the phone.
John Quinn's gigantic Oh Crap reaction when Jack flips over the trailer he's in with the backhoe of a bulldozer.
The FBI has tracked down a suspect whom they inform Jack is ex-SAS. Jack Bauer says, with complete focus, "Does he have a family?". Everyone in the room shoots him a look that's a combination of "You wouldn't" and "Oh God, he will." Jack then calmly says that he's ex-Special Forces, so he won't break unless they target his family. It's a morbid scene, but the look everyone gives Jack Bauer is priceless.
Tim Woods: The doctors are surprised [Hodges] pulled through.
Allison Taylor: That's because they never met the son of a bitch.
Directly afterwards, the secretary calls to report that Agent Walker and Jack Bauer are on the line. The president tells her to put it through before she can even finish.
Watching two not-very-bright characters trying to rob a warehouse with assistance from a Voice with an Internet Connection is hilarious. They start to panic when the codes don't open the door, only to find out they were at the wrong door. "3101. This is 3110." Cue the most impatient and priceless "OMG you idiots" expression from Dana Walsh.
Episode 22, when a cocky Charles Logan spots a renegade Jack Bauer, armed with an assault rifle and wearing a body suit (complete with blast shield face mask and kevlar). Logan's 'oh shit!!!!' expression said it all, but his exasperated cries of "IT'S JACK BAUER!" made an already amusing (and completely badass) moment downright hilarious.
That was quite possibly one of the greatest moments in 24. Logan nearly in tears was just the icing on the cake!
Live Another Day (Day 9)
At the end of Episode 3, Jack realizes he needs a diversion in order to enter the US Embassy. So he discreetly shoots some unlucky protesters in the leg and screams "THEY'RE SHOOTING AT US! THEY'RE SHOOTING AT US!" It works, and it makes for a darkly hilarious final scene.
After Adrian apologizes for screwing over Jack:
Adrian: You don't need to keep reminding me of it.
Chloe: Actually, I do. I'm thinking every day for the rest of your life.
Day 9 is darkly meta-funny when you think about it. In this season, people actually do the things they need to do. Examples follow:
When Morgan finally gets the evidence about Al-Harazi's drone hijacking plot, his boss connects her to the chief of staff, who connects her to the president, who orders all US drones to be grounded right away. You won't see this in the other seasons.
Nearing the end of episode 6, M15 officers interfere just when Jack's arms dealer is about to plug in the virus that will allow the good guys to track the bad guys. It looks like this whole episode will amount to naught and we'll have to wait another week to see what other play Jack can come up with... But no, at the end, Jack manages to hit the enter button. Really.
When Steve Navarro is discovered to be a mole, he tries to escape by telling a security guard to lock down the building. Jack then doesn't even try to reason with the guy, and just knocks him out.
Morgan injects herself with prophynol so that Jack's contacts can't interrogate her. Turns out they have drugs that can wake her up anyway. The Oh Crap on Jack's face is priceless.
While trying to evade a missile launched from a drone, Jack forgoes the badge in a Flashed Badge Hijack and just punches a civilian and takes his vehicle without saying anything!
President Heller secretly agrees to Margo Al-Harazi's demand and gets Jack to take him to Wembley Stadium to be killed. First, Jack takes out his tracking device in his arm. Heller winces in pain:
Heller: "Yikes! Ow!"
Later, a Secret Service agent sees them sneaking out. While Heller tries to make an excuse, Jack comes from behind and punches him out. Heller is taken aback:
Heller: Jeez, Jack!
Stephen Fry's marvelous reaction when Heller returns from his attempt to sacrifice himself to end the terrorist threat, and tells the Prime Minister he's sure he would have done the same for America. Earlier in the same episode, he says nothing can cause people to panic like the instruction to remain calm, which was a reference to the famous British 'Keep Calm' posters from WW2, which have attained Fauxtivational Poster status lately.
If you're a Game of Thrones fan it was fun for a change and less traumatic to see Michelle Fairley die just after first watching her son be killed, a second time now that they're both villains!
Also that she was thrown out of a high window like her son Bran Stark in the very first episode of Game of Thrones.
And that her daughter Simone looks a lot like Sansa Stark!