8mm: The killer lives with his mom, who is completely oblivious to his problems.
30 Minutes or Less: Dwayne still lives in his father's estate, watching TV and goofing around instead of doing anything productive. His father even calls him out on this.
Alvin and the Chipmunks: The Squeakquel: Dave's cousin Toby lives in his grandmother's basement and plays video games all day.
Baby Boy: Jody's mom calls him out for being a grown man living at home until he points out that she never moved out and simply inherited her house from her own mother.
Badly Drawn Roy: Roy continues to live at home because he can't hold down a job despite being in his thirties, which causes friction and arguments between him and his parents as well as running away from the camera. He eventually checks himself into a rehabilitation center because of his depression.
Best Player: The male protagonist lives with his parents in spite of being an adult until they decide to sell their house. He must win a video game tournament to be able to buy the place.
Bring Me the Head of the Machine Gun Woman: Santiago lives with his mother. While he has a job as a DJ (which his mother disapproves of), the rest of his life seems to revolve around video games, with his ambition being to create the world's most awesome video game.
The movie Failure to Launch deals with a group of grown men living with their parents who exhibit stereotypical nerd behavior. Subverted though, in that the "nerdiest" of the group actually owns the home he lives in, and took in his mother because that's what you do when your mother has nowhere else to go. In fact, everyone in the group but the main character has some sort of technicality that makes them not really live with their parents, which is used to explain why only said main character is attacked by chipmunks and dolphins.
Eric: Your mom said, "Clean up this shithole, or no grilled cheese for a week." Hutch: That's emotional blackmail, and you know it! Hutch's mom: Screw you! Hutch: I will sue you! Renter's rights! Hutch's mom: You don't pay rent!
Free Guy: One gamer by the name of Revengamin Buttons has an encrypted file in his hideout that shows proof of Life Itself existing in the game's Code. After Guy becomes an internet sensation, he ends up confronting the player, who is shown to be a 22-year old who lives with his mom.
Buttons: Mom, do you have to vacuum right now? I'm saying my catchphrase! You're ruining it for my viewers, God! Button's mom: You're 22 and live in my house, there is no God!
Subverted when Jason Nesmith is contacted by the Thermians. He thinks that they're particularly rabid fanboys who have built an exact replica of the Protector in their parents' basement. He's only two-thirds right.
Guy Fleegman, whose character played a Red Shirt in the in-movie TV-show, can be spotted in one scene hitting on a young woman who responds with "but you live with your mom!"
The Hangover: Manchild Alan refers to himself as a stay-at-home son. Even his dad thinks it's ridiculous that his 42-year-old son is still living at home. He gets his meals served to him in his room by his mother.
Subverted early into Harvey. Myrtle Mae complains to her mother about how her uncle Elwood does nothing but lounge around the house all day and still lives with his older sister. Veta promptly corrects her that Elwood inherited the entire family fortune so they're the ones living with him.
At the beginning of Hot Tub Time Machine, Jacob lives in his uncle Adam's basement and refuses to get a job or do anything with his life.
Jane Wants a Boyfriend: 25-year-old Jane lives with her parents. When her parents move to New Jersey, she moves in with her older sister instead.
Keep the Change (2017): David is an unemployed aspiring filmmaker who lives with his parents.
Lizzie Borden's Revenge: Bobby still lives with his mother, in her basement. He is very defensive about it:
"I don't live in her basement! I live in a room! That happens to be in her basement."
Mallrats: Comic-loving slacker Brodie lives in his mother's basement. His girlfriend dumps him for this reason.
Men in Black II: Agents J and K get intel from a conspiracy theorist guy who lives in his mom's attic. They claim to be from his therapy group. They end up convincing him to move out after deneuralizing him.
Most Likely to Murder (2018): Duane lives with his mother and sister, despite working as a realtor. Lowell also lived with his mother before her death.
Subverted in Of Dice and Men. John Francis lives in his mom's basement, but he doesn't have any of the social problems normally associated with the trope, and he's about to move out in order to take a job offer in another town.
Grandma: Ludlow! Did you get me some diet root beer while you were out? Ludlow:(to Brenner) You remember my grandma. Brenner: Sure. Ludlow: She's still a character after all those years. (to his grandma) No, no, Grandma. It's-It's funny. I didn't get a chance to, because, um— Oh, what happened? Oh, I remember now. I'M TRYING TO SAVE THE WORLD FROM ANNIHILATION! ARE YOU NUTS?! YOU CRACKER! Grandma: Don't yell at me!
Saturday Night Fever: Tony lives with his parents, even though his mother wants him to move out and become a priest like his older brother Frankie. He does end up moving out eventually to live with Stephanie.
Save Your Legs!: Teddy is living in his mate Stavros' garage. Stavros' wife does not approve of this arrangement.
Sing Street: Brendan dropped out of college and is reduced to staying in his parents' house.
Snatched (2017): Jeffrey Middleton is a middle-aged shut in who lives with his mother Linda and is too terrified of germs to leave the house.
Step Brothers: Dale Doback and Brennan Huff both live with their single parents (Dale with his widowed father and Brennan with his divorced mother). The plot of the film kicks off when Dale's father marries Brennan's mother.
At the beginning of The Story of Luke, Luke is an unemployed 25-year-old living with his grandparents. It isn't until his grandmother dies, his grandfather is placed in a nursing home, and Luke is forced to move in with his horribly dysfunctional relatives that he really starts looking for a job.
Tanguy: The whole plot involves exasperated parents who try to get their grown son (the title character) to move the hell out so they can have their own lives back. This French film appeared to have hit a chord with the public, as the name "Tanguy" has basically become a generic word for Basement-Dweller in French-speaking countries, where it's not uncommon to hear people complain that their son is a Tanguy.
Wayne of Wayne's World. In the second movie, he and Garth move into their own place.
X-Men: Apocalypse: Peter Maximoff is around 27 years old in 1983, and he still lives in the basement of his mother's house. In his case, it probably has something to do with his Super-Speed and petty criminal past making it very hard for him to find a plausible means of self-support; he's very self-deprecating about his situation and jumps at the chance to start attending Xavier's school.
