Just about anything involving Hex, given that she straddles the line between hilarity and terror. In particular, the exchange between her and Bob where she reveals the truth about her relationship with Megabyte.
Hexadecimal: We are from the same viral strain.
Bob: The same family?
Hexadecimal:(dramatic) Oh, much worse than that, Guardian. He's my brother! (Maniacal Laugh)
Bob: But you're always trying to destroy each other!
Hexadecimal:(casual) Oh, that's just sibling rivalry.
"Nullzilla" and just about everything involving the Humongous Mecha that the cast are given to fight it.
This exchange from the same episode:
Hack: We're looking for a null.
Slash: That's right, uh, have you seen one?
Mike: Have I seen one? Have I seen one?! ...That's a joke, right?
Hack: Hey, whadya mean "joke"?
Slash: Joke. Noun. Something said or done to cause laughter, something not in earnest or ridiculous.
(Hack and Mike just stare at him)
An earlier exchange from the same episode:
Hack:(to Megabyte) You rang, your hugeness?
Slash: All ready and waiting, oh evil one! Oh! (to Hack) Did I say "evil"?
Hack: Oh, what a giveaway.
Slash: I said "evil" once but I think I got away with it.
Hack: You said it three times!
Slash: What, "evil"?
Hack: That's four!
Slash: Oh, I hate that.
The moment when Nibbles "runs" away:
Slash: What a good boy. Look, now he is going for a walk.
Hack: Uh, what phase number is walking Nibbles?
Slash: Dahh... there is no number for walking Nibbles.
Really, pretty much any time Hack and Slash are on-screen in "Nullzilla" are CMOFs. Another example is when they reluctantly travel to Lost Angles to look for Nibbles before going into "camouflage" mode (complete with Hack being unable to pronounce the word "camouflage" and settling for "stealth" instead) - made even funnier by the fact that it is so garishly coloured it can barely even be called camouflage (though they were likely disguising themselves as Nulls, who do have those color schemes). And then Slash starts singing "I don't like L.A...".
Phong: Do not worry. I have prepared something for just such an emergency. Bob: You're prepared for a giant monster made entirely of nulls STOMPING AROUND MAINFRAME? Phong: That is correct! Bob: How do you plan for that? Phong: Ah, lucky guess?
This song from "Between A Raccoon and A Hard Place".
"Glitch! Um...anything!" Glitch then turns into a lamppost, which Megabyte slams headfirst into, flooring himself.
Apparently Glitch comes with censorship powers: as Bob is jumping off the Dragon piloted by Al and his waiter in "Quick and the Fed", just before nearly crashing through the stained glass window, he shouts "Glitch, B S 'n' P!", separating the pieces of glass to create a safe opening and then rebuilding them after he's jumped through itnote The Broadcast Standards and Practices specifically stated Bob was never allowed to crash through glass at any time.
This great variation on the "This is bad. This is very bad!" Catch Phrase:
Phong: This is bad.
Bob: Is it... very bad?
Pretty much everything revolving around Megabyte's spies and their ridiculous Spy Speak and disguises.
At one point, Megabyte stops being annoyed by the Spy Speak and just electrocutes the spy with a push of the button.
Late in season three, Megabyte walks in on Herr Doktor tucking into a sandwich as he's working. Cue the latter's highly unconvincing attempts to cover up the fact that he's eating said sandwich.
Hack and Slash recovering Phong's body for him:
Hack: Ooh! We found it!
Slash: Yes we did.
Hack: It was in the trash—
Slash: I tripped over it.
Hack: And it smelled...
Near the beginning of "The TIFF", when Bob and Dot start arguing, the camera focuses on a group of binomes, who are quietly sitting there, watching them argue, whilst eating popcorn. Cecil is also watching intently. After a few moments, Cecil actually steals the zero binome's popcorn and also starts eating.
Bob is working on his car. While singing along to some music. He turns around and the software pirates make off with Glitch (which was on the table)and whatever else that wasn't bolted down, including his car. The look on his face when he turns around is priceless.
After intentionally letting a User win a game in "System Crash", the main cast decides that all they can do is wait.Suddenly...
Bob's saved the system from crashing, he and Dot are about to FINALLY kiss after three season... And then that cockblocking raccoon appears from no where and kisses her instead.
Rocky the Rabid Racoon: The girl's tasty, but where's all the food?
From the same episode, we get this gem from Dot.
Dot: I don't even want to think about that...I mean what kind of sick creature gets enjoyment out of playing this sort of game?!
(Dot and Enzo turn to face the Camera, looking directly at the viewer with angry expressions.)
Bob in web disguise walking down the pirate ship stairs to see AndrAIa, Frisket is growls at the 'stranger'. Bob says "Hi Frisket," causing Frisket to pause, sniffs... and resumes growling. Bob shrugs, his pose practically shouting "typical."
The entire scene where the Web Riders party with the binome pirates. The best part when the surfer bumps into Matrix and he reacts instictively with violence, the Surfer tries to speak in web language to calm the Web Riders. The Surfer ends up saying, "Handbag... Teakettle... Barbeque..." The Web Riders are smart enough to figure out whats going on and not make the situation worse.
A ploy Megabyte couldn't have honestly expected to work when he hires Mouse for a job in "The Great Brain Robbery."
Megabyte: Really, Mouse. Who do you trust more... Bob or me? *Slasher Smile*
Mouse: That's it. I'm pulling the plug.
Earlier, Matrix and Turbo had blown apart some of the infected Guardians drones after asking "Do your drones have personality chips?" (or, in plain DOS, are your robots sapient). Later, AndrAIa and Frisket meet the Guardian leader. Frisket growls and AndrAIa translates: "He was wondering if your drone has a personality chip." The drone flees.
And then, disappointed, Frisket drops to the ground, looking bored while AndrAIa and the Guardian have an Old West style showdown.
Hexadecimal in 'Daemon Rising,' and her blatant affections for Bob. Two in particular, the look on her face and her extremely put upon "Hello, Dot" when Dot checks in on Bob once the invading Guardians are gone and finds Hex draping him over her and this immortal line:
A group of Daemon's infected servants, all wearing Spawn-esque masks, rise behind Daemon... and break into a celebratory gospel song about the Word. With Mike the TV on lead vocals.
Megabyte asks Herr Doktor how long they can keep Hexadecimal tied up. The good doctor is so unsure about the variables because of Hex's power and her messed up mental state that he proposes that Hex is already capable of escaping, but doesn't because she actually likes being tied up. Megabyte doesn't even want to think about that.