The Russian Roulette game in the basement is a shout out to the end of The Deer Hunter.
The same episode also alludes to Dog Day Afternoon, when Charlie chants "Attica, Attica!"
The ending of "The Gang Gets Held Hostage" has Frank in Die Hard's John McClane's role with a pistol taped to the back of his head, and he even tosses Liam McPoyle off the roof of the pub like Hans Gruber. His line, "Yippy-kay-yay, Mister Falcon!" is the dubbed line from the edited-for-television version of the film that replaces "Yippy-kay-yay, mother fucker!"
"The Gang Solves the North Korea Situation"
Frank, Mac, and Dee hold auditions for a talent show, where they take on the personae of the American Idol judges, complete with the red glasses of coke.
Frank is put into a mental institution that is an homage to One Flew Over the Cuckoo's Nest. There is even a large mute Native American. Frank escapes the mental institution in the same way the Chief does in the book. The actor playing the Chief in the episode is the movie actor's son. This doubles as an Actor Allusion, since Danny DeVito was in the original film.
Mac wants to show the Mexican family they accidentally kidnapped Apocalypto and references the racist themes that critics accused it of having upon its release.
In "Charlie Has Cancer", Artemis frequently mentions and acts out scenes from Coyote Ugly. In what doubles as an Actor Allusion, Katlin Olsen (Sweet Dee) had a minor role in the film.
In "Charlie Got Molested", Mac can be seen wearing a jacket that say "Shermer H.S." This is alluding to the fictional high school used in the John Hughes-verse. According to the commentary, the crew selected it from the costume department without realizing that it was a reference and only learned about it after the episode was filmed.
"The Gang Gets Invincible":
The film Invincible is frequently mentioned, to the point that the episode could be considered an Affectionate Parody. Everybody seems to call the film, "That New Kids on the Block Movie," apparently mistaking Mark Wahlberg for his brother, who was in the music group.
Geoffrey Owens plays himself masquerading as football player Donovan McNabb. The gang recognizes him from his recurring role on The Cosby Show, and the coach makes it a point to insist he's "not the guy fromThe Cosby Show."
"The Gang Wrestles For The Troops" makes a few references to the WWE, most notably Hulk Hogan.
"Bums: Making a Mess All Over the City"
Charlie makes repeated references to Serpico, dresses up like the title character, and tries to do an Al Pacino impression.
Dennis names the cat Special Agent Jack Bauer after the character from 24.
Frank keeps editing parts of Rambo's life into his own past in "Mac & Dennis: Manhunters".
Mac and Frank losing their precious rum ham is a reference to Wilson in Cast Away. It even has a face on it. Immediately after it floats away, the show cuts to Dennis and Dee at an amusement park called "Castaway Cove."
In "Frank Sets Sweet Dee on Fire," the guys go to Chinatown and are surprised that it's nothing like the scenes from Big Trouble in Little China.
In "The ANTI-Social Network", while looking for a Dylan Tobak they found on Facebook, Mac and Dee discover that he's actually a fictional person made up by a woman named Catfish.
The Halloween Episode "The Maureen Ponderosa Wedding Massacre" contains a reference to Jaws, with Charlie delivering a modified version of Quint's USS Indianapolis speech (regarding rats, Charlie's bete noir, instead of sharks). The homage includes Charlie adopting Robert Shaw's mannerisms, as well as the appropriation of entire lines, referring to the "black, lifeless eyes" that "roll over white" when a rat bites you (this is referenced by Dennis, who snaps Charlie out of it by directly questioning "is that the speech from Jaws?").
In "Charlie Rules the World," Charlie meets a girl from an fantasy MMO named "Queen of Thrones." This is almost certainly a reference to Game of Thrones. It helps that Charlie goes into Manipulative Bastard mode once again, and it's glorious! Before the Downer Ending, it's very clear to the Gang that Charlie has them all by the throat.
In "Frank's Back in Business," Frank and Charlie wear outfits and hairstyles ripped from Gordon Gekko of Wall Street.
In "Dennis Reynolds: An Erotic Life", Dee walks around Charlie's apartment complex and comes across twin girls who say "Come play with us. Forever, and ever, and ever," which is an homage to The Shining.
"The Gang Gets Trapped"
When Frank is about to get caught he hides in a cupboard filled with stuffed toys leaving his face visible, like in E.T. the Extra-Terrestrial.
And of course the repeated references to Indiana Jones, right down to the hat and whip.
"The Gang Saves the Day"
Charlie's fantasy is a reference to the opening montage in Up.
In Dee's day dream, she becomes famous by playing a British male butler, referencing Mr. Belvedere.
In "The Gang Beats Boggs", Dennis gets off the plane in North Dakota, referencing Glenn Howerton's turn in Fargo. Fargo is also on the map that shows up in the episode.
Dennis's analysis of the lonely woman on the plane is a series of deductions ripped straight from Sherlock.
At the end of "The Gang Buys A Boat", the inflatable flailing-man continues to dance as the boat burns and sinks. This is highly reminiscent of the end of Moby-Dick, where Captain Ahab is lashed to the flanks of the whale and it seems he is beckoning the crew of the Pequod on to their doom.