A classic tactic of psychological warfare.
You've just met someone. They don't know what to make of you. They happen to be eating at the time. What do you do?
Take their food. It's a step beyond just invading personal space, and it shows who the alpha dog is.
May overlap with The Snack Is More Interesting and Lost Food Grievance.
Tubby and Willy both do this to Lulu in an episode of the Little Lulu anime, with a tray of sandwiches that Lulu was preparing to have.
In Death Note there is L's (cat)fight with Misa. "You can call me whatever you like but I'm still taking your cake."
Mugen dugs in uninvited to the lunch of some Yakuza thugs. When the predictable reponse follows their boss is so impressed by his badassery he invites him for dinner.
In Sailor Moon Stars, when Sailor Aluminium Siren and Sailor Lead Crow attack a TV show host who arrived to Usagi's house under the guise of a pizza delivery guy, Siren's first action is... to eat one of the pizzas, much to Lead Crow's exasperation.
In Pokémon, the Squirtle Squad make their debut by beating up Team Rocket and eating their lunch right in front of them.
In Naruto, Jirobo delays delivering a finishing blow to Choji long enough to take and eat Chouji's last bag of chips in front of him.
In episode 5, season 1 of Love Live!, Nico swipes Honoka's and Umi's fries, but is caught when trying to steal Honoka's hamburger. When Honoka demands her fries back, Nico defiantly opens her mouth, causing the former to clarify by having her buy new fries.
In one Birds of Prey story, Black Canary and Wildcat are having lunch in Singapore while pretending to be drug dealers as part of a plan to prevent a drug shipment from reaching Gotham. A detective, thinking they really are drug dealers since they were seen in the company of a notable suspected (as in everyone knows but there's no concrete evidence) drug dealer, sits down and helps himself to some of Dinah's chili crab and tells them they should leave Singapore immediately and never come back.
In Interstitium, Grunt falls in love with the whole concept of flavor and becomes a Big Eater, wanting to taste everything. During their first mission, he tells Garrus he doesn't have any problem with him, but will unless he hands over his rations. Garrus incredulously points out that it's dextro-formulated and will just make Grunt sick, but hands it over anyway to avoid a fight. (Then laughs to himself when he does wind up sick.)
A variant comes into play in This Nearly Was Mine, more of invading one's personal eating haven being violated than actually eating food. Frederic Horshoepin still harbors lingering resentment towards Vinyl for stealing the mare of his dreams, so her venturing into his favorite restaurant, chatting like they were old pals, decrying his choice in food, and talking about "'Tavi" in front of him certainly irritates him.
The Death Note fic Seigikan opens with one ineffable genius mind game between Light and L where Light steals and takes a bite out of one of L's strawberries and then L steals the half-eaten strawberry back and eats it.
The most famous fictional example is probably in Pulp Fiction. When Jules and Vincent bust into the preppies' hideout, Jules asks Brett—in a way that really isn't asking at all—if he can have his burger and soda. Brett and his gang never recover. The best part is that while Jules is drinking Brett's soda, he's staring at Brett the whole time, with this expression on his face that pretty much says "Yes, I am drinking all your soda, and you're not gonna do a damn thing about it." You also hear that slurping sound from the straw as he's drinking the soda, which we all know means he drank the whole thing.
It's a Discussed Trope in True Romance, also written by Quentin Tarantino. When Clarence confronts Drexl, Drexl tells him that he should have grabbed some food and sat down to watch the movie playing in his lair. That way, Drexl would have thought him a badass.
In the Disney Channel Original Movie Brink, the main characters find this happening to them all the time. They get revenge, though - they stuff a sandwich full of worms, and when the big bad eats it, he gets a nice mouthful of the little wigglers. Revenge is a dish best served...with worms.
When The Joker crashes Bruce Wayne's party in The Dark Knight, helps himself to a shrimp kebab and then grabs a glass of champagne from a guest, quaffing it with great gusto before replacing it on a stack of wine flutes.
An example from Machete: after capturing the priest, Booth helps himself to sacramental wine and sarcastically remarks that "God's blood tastes like Merlot".
Played with in A Fish Called Wanda, where Otto torments K-k-ken by eating a number of his beloved pet fish... alive.
A variant of this happens to Timmons, the wagon driver who transports Lieutenant Dunbar to Fort Sedgewick in Dances with Wolves. After he's killed by a Sioux war party, one of the party is seen eating Timmons' beloved pickled eggs.
Pan's Labyrinth offers a post mortem example: The Captain takes killed hares or rabbits after killing an innocent hunter and his son.
Happens in Romy And Michele's High School Reunion, after Christie covers Michele's back with magnets and takes Romy's burger. Funnily enough, the titular girls don't realise this is a power play at first.
In Men In Black II, Serleena interrogates the pizza parlor owner actually the alien protecting Laura, the Light of Zartha for the location of the Light of Zartha. When he remains Defiant to the End, she kills him. Then she takes a pizza to go.
In a discussion of vampire folklore, one author noted a tale in which a bloodsucker invited itself into some villagers' home just as they were sitting down for dinner. It came in, sat at down at their table, ate all of their food off their plates (even sucking the marrow out of the bones) and then left without saying a word.
In the Peter Straub story Mr. Clubb and Mr. Cuff, a rich man hires two eccentric hitmen to kill his wife and her lover. When they arrive at his home, they quickly polish off his lavish breakfast and tell him to make himself some toast.
Arthur Dent tells an anecdote about this in So Long, and Thanks for All the Fish, which the author, Douglas Adams, claimed to have experienced. After purchasing a bag of train station biscuits (cookies), Dent sits down at a table with a stranger and reads a newspaper. The stranger reaches over, opens the bag, and eats one of the cookies without comment. Dent, stunned, can only react by eating one himself. The two men go back and forth eating the cookies without comment until they're all gone, and they exchange meaningful looks before the man leaves. Only when Dent himself prepares to leave does he pick up his newspaper and discover his own unopened bag of biscuits.
One of the first affronts committed to Horatio Hornblower as a midshipman by the senior-most midshipman was his tendency to help himself to pieces of the other midshipman's food — right off of their plates. The antipathy between them eventually reaches the point where Horatio challenges the other man to a duel.
Burke advises the nephew of a friend how to survive in prison, as well as paying the prison Big Bad to protect him. When someone tries intimidating the kid during lunch and the Big Bad steps in to stop it, the kid deliberately grabs the cake off the man's plate and eats it.
In Red Dwarf, Cat steals French fries from a fellow inmate in the hopes that he will be hospitalized for his troubles. Instead, it backfires hilariously and the inmate swears to become Cat's bitch.
House steals Wilson's food repeatedly - for laughs. This is along with bigger versions of the same thing, such as getting him to lend him money and not repaying it. Eventually he admits that he does it as a way of quantitatively testing their friendship. Awww...? Wilson later claims that he does the same by telling flattering lies to House, gauging to see how blatant a lie House will accept as an honest compliment before he catches on. There is also the time when Wilson's complaining about this served to trigger House's Eureka Moment. Turns out the patient had an intestine parasyte that was eating the medicine and generally messing up the tests.
Awesomely parodied by Stella, which includes a scene where Michael attempts to psych out his enemy by eating his ice cream cone in an intimidating fashion. Macho posturing and eating ice cream cones do not go well together.
Saturday Night Live parodied the famous scene in There Will Be Blood by having Daniel Plainview host a Food Network show in which he visited malt shops and literally drank people's milkshakes.
In a Chappelle's Show sketch, Wayne Brady acts like a violent psychopath and reduces Dave Chappelle to tears. Then he takes Dave's food after they grab some from a drive thru.
Happens frequently on Klingon vessels in the various Star Trek series.
Not quite as rude as stealing from someone's plate, but federal flack Twitchell on Tremors: The Series was always taking food and soft drinks from Jodie's store without paying for them, in one of many ways he threw his weight around.
Oz. Inmates do this to other inmates they can intimidate, usually leading to much worse things.
On ER, our first introduction to antagonist Kerry Weaver is when she eats several of Mark Greene's French fries (he was interviewing her over lunch). Although she does ask for them rather than taking them outright, indicating that she's merely clueless rather than outright malicious, she does proceed to be a thoroughly irritating thorn in his and practically everyone else's side for the next 12 years.
In Doctor Who, the Third Doctor duels with the Master with swords. During the fight, he proceeds to steal the Master's sandwich and eat it in front of him.
The Americans: In the pilot, after a child predator makes crude remarks about his daughter, Phillip catches the guy barbecuing in his backyard. Phillip beats his ass, threatens to kill him if he catches it happening again, and then walks away with a hot dog off of his grill.
Parodied in Justified. Dickie Bennett, looking to build his reputation after being cut off by his mother, steals food as part of an attempt to intimidate Boyd. As it happens, Boyd and his henchmen were just discussing who they can target to establish themselves as being back in the criminal game. Dickie's pathetic attempts are seen by Boyd as good fortune, and he can't stop laughing when Dickie tries.
In "The Even Chance", a very well-written and excellently performed hissable villain Jack Simpson is a twisted bully who torments his fellow midshipmen. He steals Horatio's mutton and drinks from his mug in his very first scene.
Horatio: What do you mean by helping yourself to my vittles, sir?
Jack Simpson: I should have thought my intention was quite obvious.
In "Mutiny", a jerk of a sailor Randall tries to take Styles' mug from the table, but Styles manages to make him put it back.
In The Office (US), Michael, Pam and Ryan have returned from the Michael Scott Paper Company, and the others are jealous that they are getting special treatment. They have a secret meeting in the warehouse, saying it was their lunch break. Michael then proceeds to take their real lunches out of the fridge and eat them in front of the others with Pam and Ryan.
Game of Thrones saw The Hound calmly chug down Polliver's mug of ale when Polliver started getting confrontational. Bar Brawl ensues. With swords. Later on after Arya kills a bunch of Frey bannermen as he chastises her ("next time you do something like that warn me") he can be seen sitting down at their camp eating their food.
The song "Haunted House" sung by Jumpin' Gene Simmons (not that one):
In my kitchen my stove was a-blazin' hot.
Coffee was a-boilin' in the pot.
The grease had melted in the pan.
Had a hunk a-meat right in my hand.
From outer space there sat a man
On the hot stove with the pots and pans.
"Say that's hot" I began to shout.
He drank a-hot coffee right from the spout.
He ate the raw meat right from my hand.
Drank the hot grease from the frying pan.
Looked at me said "You better run.
"And don't be here when the mornin' comes."
In one Peanuts strip Linus is asking, "Who took my group of grapes?" Lucy corrects him that it's called a "bunch" of grapes...as she eats his grapes right in front of him. Then she tosses the emptied grape tendril at him as she leaves.
In one Calvin and Hobbes strip, Calvin is eating his lunch, only for Hobbes to swoop in, beat him up and take his lunch.
In Garfield, pet cat Garfield constantly steals Jon's food.
There is an urban legend circulating in many a country, known at snopes.com as "pinched cookies". A stranger comes to an old lady's table at a cafe and keeps helping himself to what she thinks are her cookies. When the stranger leaves, she finds out her cookies are unopened.
The Sandvich. Specifically, if a Heavy is carrying his Sandvich when he dies, he will drop it, and anyone who runs it over, even enemies, receives 50 health. The Scout has a voice response for this that alludes to the (in)famous milkshake analogy from There Will Be Blood:
He does the same thing in Meet the Scout, when he interrupts a Heavy eating a Sandvich, kills him, and steals it. The Heavy gets vengeance in Meet the Sandvich. Because of this, Scouts actually gain a little bit more health (75) than the other classes if they grab a stolen Sandvich.
Scout "Ahhh, my blood! He punched out ALL MY BLOOD!"
Incidentally, the Heavy has an achievement relating to this occurrence, called "Don't Touch Sandvich" which involves killing a number of scouts with a specific weapon. The scout on the other hand, gets an achievement for taking the Heavy's sandvich ("Dodgers 1, Giants 0").
Soldier also has a similar line after dominating an Engineer:
Soldier: I will eat your ribs, I will eat them up!
Mid-Boss steals the lunch that Flonne and Jennifer made for a picnic in Episode 10 of the first Disgaea game. When they finally catch up to him, he's eaten it all.
Any videogame where you can loot your enemies and their hideouts and occasionally find food, like in Fallout or BioShock, think about it.
During a party in Mass Effect 3: Citadel, Garrus and Zaeed decide to start "preparing" Shepard's apartment in case someone else tries to steal their life. One of their ideas is to rig the coffeemaker to dispense poison and/or explode (their opinions vary as to what would be most effective) in case anyone tries this trope. Shepard is skeptical about this whole plan, to say the least. The whole thing is probably a sideways reference to the Deception example, above; it even takes place in the same apartment.
Pinocchio: Honest John takes the apple Pinocchio is bringing to the teacher and eats it as he talks him into becoming an actor instead, then gives him the core.
The Princess and the Frog: Big Daddy is eating beignets when Charlotte comes in gushing about Prince Naveen and keeps taking them out of his hands as she plans on how to get the prince to meet her.
In an episode of DuckTales, the Beagle Boys torment Doofus by eating his pancakes.
In the first episode of TaleSpin, Don Karnage intimidates the customers at Louie's by drinking someone's drink.
In Kung Fu Panda, this is the strategy that Master Shifu eventually hits on as the best way to motivate Big Eater Po. He gives Po a bowl of dumplings and deftly snatches them away from him before he can eat them. Cue a Training Montage of the two Chopstick Fencing over dumplings.
Subverted in an episode of Teen Titans, where Cyborg infiltrates the H.I.V.E. disguised as "Stone". In the cafeteria, both Gizmo and Mammoth try to intimidate him, Mammoth taking his hamburger and eating it to do so. It fails to intimidate him at all; he quickly assumes a stone-like form and crushes the table, elicting nervous laughs from both of them.
In the Batman: The Animated Series episode "Critters", Farmer Brown sends a talking goat into the police station to deliver an ultimatum to Commissioner Gordon, and it eats Harvey Bullock's donut on the way in. (Bullock is very angry at first, but then he finds out that the goat can talk and the rather serious nature of the threat, and forgets about it.)
In The American Civil War's Battle of Shiloh, early in the battle, after the Confederate attack had sent Union troops fleeing from their camps in panic, the hungry Confederates stopped to eat the food they found in the camps. This delay actually helped save the Union army. This makes sense. The Confederate army was infamously and severely underfed because of a crippling lack of food and supplies. They basically didn't have to waste any of what little energy they had, and with a hot, delicious, freshly made breakfast just sitting there, right in front of their underfed faces, well... Anyone who wouldn't take advantage of this after being damn-near starved, is too dumb to live.
The 'Battle of the Sausages' during the Winter War between Finland and the USSR: the Finnish troops, knowing the poor state of supply of the Red Army, deliberately set up and abandoned a field kitchen, then ambushed the enemy soldiers who inevitably stopped to help themselves.
During late stages of World War II, especially during the Battle of the Bulge, the most prized item that Germans captured from US troops was the food, as indicated on this website as Germany was running out of food to feed its soldiers and civil population.
Chopper Reed, an infamous Australian standover man (extortionist) turned public speaker has told a tale about how he once cooked a man's dog on the man's barbecue grill, ate some of it, then forced the man to eat the rest.
The Duke of Wellington ate Marechal Jourdan's pre-prepared "victory feast" at the Grand Hotel after the Battle of Vitoria in The Napoleonic Wars. Graciously, he still paid for it.
Averted by a war correspondent who came across an abandoned yet fully laden table in a German officer's barracks in recently liberated France. Having been briefed of the Germans fondness for Booby Traps, he ignored what seemed like obvious Schmuck Bait. The next day he had to listen to one of his colleagues boasting about what a great meal it was.
Eric Harris and Dylan Klebold, the killers at Columbine, apparently stopped to take sips from students' drink cups left behind in panic in the cafeteria after the shooting started.