The end of "Charlie Goes America All Over Everybody's Ass". After turning Paddy's into a bar with absolute freedom, Frank gets sent to the basement to run his gambling operations. After deciding to evacuate everyone, Dennis and Mac go to the basement to find that Frank has spread his gambling to Russian Roulettea laThe Deer Hunter. He spins a revolver and gives it to a participant, off screen we hear a gunshot, and a thud. The fact that all of Frank's "friends" in that basement are Vietnamese, along with the fact that Frank is wearing a pair of sunglasses with one of the lenses popped out and smoking a cigarette while doing this, makes that scene also a Shout-Out to the most famous scene from the end of The Deer Hunter.
The entirety of "Who Pooped the Bed?", especially Dee's Freak Out! over poop at an art gallery and Artemis' whodunit-style summation that turns out be as wrong as it is farfetched. Toilet Humor doesn't get much funnier than this.
The scene where the alleged scientest checks the poop.
The end of "The Gang Gives Back". To elaborate, as part of court-ordered community service for what they did to the Israeli man who threatened to take their bar, the gang (save Frank — who had nothing to do with the explosion, and Charlie, whose community service sentence is to join Alcoholics Anonymous) are required to coach dual basketball teams at the local rec center, Dennis coaching one team, Mac and Dee coaching the other. Frank decides to get in on this by betting on the game with his chain-smoking, Vietnamese friends. Only he fixed the game by giving Dennis' star player a bike to stay out of it. After realization of this disadvantage, Dennis teaches his team to play dirty, and Mac and Dee do the same. Meanwhile, Charlie was required to join an AA club, where he see the waitress and tries to stalk her there. When he lets out that Dennis is coaching a community basketball team, she attends the game to see him coach. Feeling jealous, Charlie shows up the game also, DRUNK, and apparently, as the referee. The result must be seen to believe.
Charlie's "Kitten Mittons" commercial.
Sweet Dee getting dry heaves while attempting stand-up comedy.
Charlie's and Mac's outrageously ridiculous plan to fake their deaths in "Mac and Charlie Die: Part One".
"The Gang Gets Whacked". Charlie and Dee witness Rickety Cricket upon giving him cocaine. The all-definite proof that drug use can be hilarious.
Jockey: So come on you old son of a gun - And let Buster do a line off your boner.
(Beat) Charlie breathes in, and walks away without saying a word.
Thunder Gun Express: "No surrender, no surrender, no surre-" *Sees the cops* "Oh...shit. I surrender."
Charlie's date in "The Waitress Is Getting Married". From Dennis and Mac setting him up with a Match.com profile to the disastrous ending.
In "The Gang Wrestles For The Troops", Frank welcoming Ben the soldier (who just got dumped by Dee after she saw him in a wheelchair) home by inviting him to a wrestling match, presenting him with a gift of a pair of jean shorts and awkwardly saluting him to "A Kiss From A Rose" by Seal.
The end line of "Dennis and Dee Go On Welfare": "Because you are crack heads, children."
Also, every scene with Charlie and Mac in the limousine.
The gang advising the therapist to bring a gun to Frank's intervention.
Everything Charlie says after agreeing to date a teenage gossip addict in "Underage Drinking: A National Concern", as well as the final shot of Mac showing up stag to the high school dance. (Neither of these are flashbacks.)
The boat episode where Dee dances like the inflatable dancer seen in most used car lots. When the boat goes up in flames...it's still dancing.
Not to mention the entire ""implications" discussion
The entire Road Trip episode - There's just too many to describe.
The Unreliable Narrator parts of the 2010 Halloween episode "Who Got Dee Pregnant?" - culminating with Dee as an ostrich.
Mac's letter to Chase Utley.
"We can't eat the rabbit! He's got Frank's soul!"
Charlie playing his "Nightman" song (and being oblivious to the rapey undertones of the lyrics) in "Sweet Dee is Dating a Retarded Person".
Mac: It sounds like a song where a guy breaks into your house and rapes you.
Charlie: What, dude? Where are you getting that from? It's just two men sharing the night/It might seem wrong but it's just right/It's just two men sharing each other/It's just two men like loving brothers...
The entire episode of "Sweet Dee is Dating a Retarded Person" is hilarious from start to finish.
From "The Gang Finds A Dumpster Baby":
Frank: What the hell is that?
Mac: It's a baby we found in the Dumpster.
Frank: Well put it back, it doesn't belong to you.
Ryan stabbing Liam in the arm in "The Gang Gets Held Hostage".
Liam: You were supposed to stab one of them!
Made even funnier with The Reveal that the knife's rubber.
In one episode, Dee tries to make a viral video. Something about the emphasis just perfects Mac's reaction:
Mac: Dee, there are a million videos on the Internet. Who gives a shit?
In one episode, there's a serial killer in the area hunting young, attractive blonde women, and Dee is worried that she might get attacked. Everyone claims that she doesn't fit the profile at all ("You're blonde and a woman, but that's hardly enough"), and its forgotten about. They suspect Mac is the killer (he's hiding the fact that he's dating a pre-op transsexual) so they decide to stage an intervention. But they don't want to do it at one of their places (Frank has a chainsaw he's itching to use if Mac gets feisty), so they use the apartment that Dee is supposed to be housesitting for some guy who's obviously in love with her. They go to the apartment, do the intervention, and of course it turns out Mac's not the killer. Charlie goes to see if there's any food in the fridge, and finds the severed heads of young, attractive blonde women. Then the owner comes home. The episode ends with Frank revving up the chainsaw.
The Coach in "The Gang Gets Invincible" never fails to make me laugh. He manages to scream almost every line he's got without being overly hammy, and scares the shit out of our protagonists.
In the finale of season 7, the gang go to their high school reunion, and perform "Plan B", an incredibly intricate and awesome dance number that really seems like a Moment Of Awesome for the entire gang. Then it reveals that the entire dance was a drunken hallucination in their heads, and all they did was dance drunkenly and yell in front of their entire high school reunion.
"The Night Man Cometh" all the way through.
"I WILL SMACK YOUR FACE, OFF OF YOUR FACE!!"
The part where Mac leaps in bed with Dennis and the lights go out; we hear Dennis say "Dude, do you have a boner?" to which Mac replies "Don't ruin this for me!"
"Frank Sets Sweet Dee on Fire" - the moment where...well, Frank causes Dee to catch fire as she attempts to save a box of kittens, which she proceeds to hurl because she's on fire.
And, of course, the title card, which is immediately preceded by Frank innocuously asking "How's anybody gonna get hurt?"
"Mac and Charlie Die: Part 2" - Frank playing with the Charlie mannequin and Frank imitating Charlie's high whiny voice.
"The Gang Solves The Mortgage Crisis" - This one line from Dee in the way she says it:
Dee: Ohhh shit, is that a pool?!
When the gang goes to Football tryouts, several do acid. Frank gets trapped in a bathroom and is too high to get out. He sees a woman who tells him to get out through the toilet. Later it's revealed that all of this is in his head and he's just standing in a garbage bin, asking the rest of the gang how they got into the bathroom.
In "The Gang Runs for Office", when Charlie isn't happy that Dennis decided to just drop out of being a comptroller, especially when he traded his entire "savings" to save Dennis from a smear campaign. His reaction? He takes off one of his shoes, shows it to Dennis, and proceeds to slam the shoe repeatedly against the counter top.
The entire final scene of "Sweet Dee Gets Audited", where the gang stages a baby funeral (or, as they call it, "The darkest thing they've ever done," though, given the show, it'll get worse), qualifies, from the botched Product Placement of "Wolf Cola" ("It's the right cola...for closure") to the moment where Dennis throws chili powder in Dee's eyes to simulate crying, to the moment where a dead dog found in the alley flops out of the "baby"'s casket.
In "Frank's Pretty Woman," Charlie vomits fake blood all over his date while acting as a Southern billionaire.
Charlie: I THINK I'VE BEEN POISONED BY MY CONSTITUENTS!
The 2nd song in "The Gang Tries Desperately to win an Award" when telling the guests to go fuck themselves.
The first time charlie writes a song, they expect it to be one of his usual pieces about "spiders and ghouls and rape", but it's an upbeat, Randy Newman style theme song for the type of innocuous sitcom bar they're trying to be. They still lock him in the basement. After spending the day down there with his muse: Paint Huffing, Charlie comes up to perform his song for the critics. The gang expect the middle-of-the-road theme song to smooth things over and make them look likable, until they hear the new song:
Charlie: There is a spider, spider, spider...
(The gang's hopeful looks immediately fall away)
Charlie: He's deep in my soul, soul, soul. He's been there for years. He's got a big bite. Now he's ready to fiiiiiiight! For what he loves! I don't need your trophies or your gold, I just wanna tell you all, "go fuck yourselves!"
Then the gang take it as their cue to start spitting on the critics.
The ending of "The Gang Saves the Day", after all that fantasizing about saving the day, they all decide to shoplift some groceries while the cashier is being robbed.
Near the end of the Flowers for Charlie Charlie unveils his new invention: a machine that allows spiders to talk with cats. Made even more funny when it turns out the pill Charlie was given was a placebo.
Basically every scene of Dee (and Charlie, for that matter) when they're jacked up on steroids in "Hundred Dollar Baby." The (arguably) funniest scene occurs when Dee's rival states that she "looks like a Holocaust victim wearing pageant makeup" to which Dee replies "I WILL EAT YOUR BABIES, BITCH!"
Also the scene where a crackhead mugger threatens the gang and they throw Dee to the ground and run off, completely abandoning her.
Reggie getting beaten half to death, shot and arrested in Frank's Brother every time he tries to be nice and forgiving and in the last case as he's trying to leave it all behind him and get on with his life.
Frank's statement of "Thanks to you I am no longer attracted to mules."
The ENTIRETY of A Very Sunny Christmas. Highlights include Mac and Charlie's Christmas flashbacks, Frank coming out of the coach naked at a Christmas party, Charlie attacking Santa, the gang getting trash thrown at them, and Frank's stop motion coma dream.
A lot of the arguments used in Reynolds vs. Reynolds: The Cereal Defense, but especially the entire sequence where Mac tries to explain why evolution is a lie, for the sake of maintaining credibility. Special shout-outs go to the moments when Mac says that many smart people throughout history consistently disproved several of the theories of their intellectual predecessors and consequently made them "look like a bitch!" Note that this last part is complete with dramatically slapping a sticker that reads "Bitch" over pictures of them.
What makes it funnier that a lot of these theories were disproven with science.
How can we possibly forget the glorious sequels that are Lethal Weapon 5&6?