Happosai of Ranma ½. Then again, he's been screwing politeness his whole life (except around girls he's hitting on), so his seniority is really a secondary factor. And sadly as one of the most powerful martial artists in the world, nobody can really restrain him in any way (unless they bring panties).
Deconstructed in Bubba Ho Tep, where Elvis is allowed to be as rude as he likes because nobody takes him seriously anymore anyway.
Elvis: Shit! Get old, you can't even cuss someone and have it bother 'em. Everything you do is either worthless or sadly amusing.
In The Golden Child there's the unnamed elderly High Priest, who tends to cuss and pick his nose a lot. (He does help the protagonist, thought.)
Mrs. Dubose from To Kill A Mockingbird casts aspersions on the entire neighborhood, but Atticus tells his children to leave the poor, sick, old woman alone. Then again, that probably has more to do with his general decency than anything else.
Well that and the fact that he had some admiration for her since she was addicted to morphine and trying to quit before she died of the disease she had. Dying slowly and very painfully instead of easily without pain if she had just stayed on it. That takes guts.
The poem Warning - When I Am An Old Woman I Shall Wear Purple by Jenny Joseph is about a middle-aged-or-so woman fantasizing about being eccentric when she is older and doing such things as learning to spit, swearing in the street, and picking flowers in other people's gardens.
It is worth noting that one line of the poem ("...I shall wear purple with a red hat...") inspired the whole the "Red Hat Society" thing. Lately, many products for older women proudly display a funny red hat as a symbol of sisterly unity.
The following verse by Lemuel F. Parton sounds a similar note:
I have led a good life, full of peace and quiet/I shall have an old age full of rum and riot/I have been a good boy, wed to peace and study/I shall have an old age, ribald, coarse and bloody/I have never cut throats, even when I yearned to/Never sang the dirty songs that my fancy turned to/I have been a nice boy, and done what was expected/I shall die an old bum, loved but unrespected.
Similarly, Dave Barry has written about his wish to "age dis-gracefully", hitting things with his cane, yelling at people, and generally being a bastard.
Dave also writes about seeing a senior citizen holding up traffic in New York city by standing in front of a taxicab and whapping the hood with his umbrella, over and over again. The cheering crowd around him was clearly expressing the sentiment that the old guy was doing what they'd like to do but never could.
A scene he saw at a party where an old lady innocently crept up next to some guy and speared his foot with her cane. When he tried to quietly pull free, she shifted her weight so that he was still stuck. "It made for fine entertainment and a younger person could never have pulled it off".
The Autobiography of Miss Jane Pitman told the tale of an African-American woman who joined the Civil Rights Movement in 1962 at the age of 110. She used her extreme age ruthlessly (after all, what cop, no matter how redneck, wants to be known as the one who rousted or roughed up a 110-year-old woman?).
"Gramps" (really great-great-grandpa) from Kurt Vonnegut's short story Tomorrow and Tomorrow and Tomorrow. He tortured his descendants by constantly changing his mind about who would receive his fortune. The root of the problem in the story is a medicine called anti-gerasone, which stops aging as long as it is used. This creates relative immortality; the user will live forever unless he or she stops taking it. People put off breaking their addiction to life further and further; the grandfather, for example, was 172, and was described as still in his prime.
Although it's implied that she's one of the wealthier members of the family, so that might also have something to do with it.
Speaking of Harry Potter, this trope is averted with Albus Dumbledore, who's over one hundred years old himself but always infallibly polite, even to Voldemort.
In A Song of Ice and Fire, Mace Tyrell's mother Oleanna, the "Queen of Thorns", is the only noble of a great house allowed to get away with complete and utter tactlessness - and as for the minor houses, rudeness doesn't begin to cover the ninety-year-old Lord Walder Frey. Murder does, for both of them.
Granny Weatherwax and Nanny Ogg from the Discworld books are the living embodiment of this trope, of which they are fully conscious and which they exploit everywhere. (At one point the narrator explains that they don't think of themselves as old, but they take every possible advantage of other people's perception of them as such.) Note that they have the advantage of being witches.
Likewise Cohen the Barbarian, who has the advantage of being good enough at being a barbarian hero that he survived to old age. And he has a huge sword if people don't catch the hint.
The locals might not be fooled by the witches. They certainly don't regard them as being any kind of infirm.
"You wouldn't let a poor old lady go off to confront monsters on a night like this, would you?" "Why should we care what happens to monsters?" "Would you go out on a night like this?" "Depends if I knew were Granny Weatherwax was."
Also, Nanny Ogg is the maternal ancestor to a sizable portion of Lancre.
The wizard Windle Poons from Moving Pictures. "I'm an old man, and I'm hungry!" Hells, Wizards full stop. Most of the Faculty is past retirement age.
Topsy Lavish, "a Mark One Feisty Old Lady" in Making Money, has "a forthright way of speaking which flirts with rudeness, and more importantly flirts with flirting".
Elinor from Inkheart, the old woman who is exceptionally rude and standoffish to most of the other characters. Her actions are generally accepted by the protagonists and either amuse or annoy the antagonists.
In Sandy Mitchell's Warhammer 40000 novel Scourge the Heretic, a teenaged Inquisition operative posing as a noblewoman over a century, intentionally invokes this, explaining her bluntness by saying that at her age, you realize it saves time.
Philip Marlowe's client, General Sternwood, in The Big Sleep by Raymond Chandler. The wheelchair-bound general is very frank about his daughters' outlandish behaviours and reputations, "because my hold on life is too slight to include any Victorian hypocrisy."
In the book version of Howl's Moving Castle by Diana Wynne Jones (not as much in the anime), shy, dutiful protagonist Sophie is cursed by being transformed into an old lady and immediately uses this as an excuse to be rude, obnoxious, and generally do whatever she wants. After all, the curse has ruined her life so she figures she might as well enjoy one of the few perks of old age.
The Warlord Chronicles provides possibly the best example: Merlin. Is arguably even worse than Nanny Ogg and Granny Weatherwax combined about this trope.
"What—has O-Tar seen an ulsio and fainted?" demanded I-Gos with broad sarcasm. "Men have died for less than that, ancient one," E-Thas reminded him. "I am safe," retorted I-Gos, "for I am not a brave and popular son of the jeddak of Manator."
In Robert A Heinlein's stories featuring the Howard Families, Lazarus Long gets away with a lot of rudeness and lack of tact because he's TheSenior — literally the oldest member of the human race, over 2400 years old by the time of To Sail Beyond The Sunsetnote at least on one time scale. He spends enough time on other time axes or otherwise time-traveling that it can be hard to come up with an exact figure, so 2400 is a minimum, really. Of course, he's like this even at the relatively young age of 213 at the start of Methuselahs Children.
This is the attitude most elders take in Warrior Cats. Sandstorm even says that once she becomes an elder it will be her life's ambition to be the crankiest elder who ever lived.
In The Island of the Aunts, Ursala the old mermaid does not make life for her daughter-in-law and grandchildren very pleasant. She does become very awesome when she lashes out at the sailors that kidnap herself and Queenie, screaming at them to "stop ogling my granddaughter, you plug-ugly!" and insisting that she doesn't care what they do to her because "[she's] already old!"
Live Action TV
In one episode of Malcolm in the Middle, an old lady wants Reese to give up a changing room, although he was there first. Another episode has Malcolm working for an elderly neighbor who fits this trope. The family's grandmother, Ida is made of this trope, along with Racist Grandma. She's a borderline case of Evil Old Folks.
Oscar Leroy in Corner Gas is stubborn, inconsiderate, prone to demanding the RCMP detachment arrest whoever annoys him, and browbeats every public official with, "My taxes pay your salary!" Of course, in his point of view jackasses don't deserve respect.
One of his Catch Phrases is "I'm a senior!" At one point his son points out that, since he's 63 years old, he isn't technically a senior citizen yetnote in Canada, where every second of the show takes place, 65 is that magic number, though the current government has suggested it should be raised to 67, but Oscar completely ignores this.
The Brit ComWaiting For God is largely built on this trope, although Diana Trent — the worst offender — was like this for most of her life.
Doctor Kelso from Scrubs, the Dirty Old ManDr. Jerk described by others as a product of his time, thinks nothing of being ruthlessly nepotistic towards his patients, has an apparently insatiable sexual appetite with boundaries that disturb his fellow workers (much to his amusement), and has no qualms about randomly bringing up very offensive topics during small talk, such as making extremely morbid jokes about dead patients that horrify everyone around him (much to his confusion) and casually asking others to accompany him to Donkey Shows.
It's implied that he does this simply because this is how everyone perceives him and because it makes his job easier. One episode is centered on the one day he's completely nice and willing to do things for patients because it means nobody will bother him for the remainder of the year and another episode has him being best friends with another senior doctor (played by Dick Van Dyke) who is his complete opposite.
In later episodes, after he retires, he actually admits to Dr. Cox that he likes him and they become friends. He's also a lot less mean, though he is still rather snarky and even gets away with getting free muffins every day and stealing a table and chairs from the hospital cafeteria.
In a direct use of this trope, at one point Dr. Kelso says to Dr. Cox, "Let me make this clear, Perry- I'm old, and I don't care what people think of me." Then he farts, turns around to the patients waiting in the room and says, "That was me, folks."
Lady Lavender from You Rang, M'Lord?, who throws food at the servants at least once an episode.
Blackadder the Third: "I want to be young and wild, and then I want to be middle-aged and rich, and then I want to be old and annoy people by pretending that I'm deaf".
Mrs. McClusky from Desperate Housewives doesn't bother to edit herself anymore. As such, Lynette hates her for most of the first two seasons, then grew to tolerate her.
Though not as impolite as most examples, Gus Witherspoon, the crotchety grandfather played by Wilford Brimley on the family drama Our House certainly qualifies. On one episode, he insisted the family prove they could survive without modern appliances for an entire weekend because he was annoyed at their dependence on newfangled gadgets. In another episode a group of teenage punks tries to intimidate him and he responds by telling them that at one point in WWII he actually "got fat" even though a Japanese machine gun nest overlooked the route from his usual post to the chow hall.
The episode with guest star Dizzy Gilespie introduces Astoria, Waldorf's elderly wife. She proves to be just as snarky as Statler (in fact, she looked just like Statler, but in a dress and Nice Hat).
Seinfeld's parents and Uncle Leo use this excuse to try and get away with shoplifting.
But only batteries! They're expensive, you know.
Not to mention one of Jerry Seinfeld's many bits on old people. In this one he comments on how it seems that, once people reach a certain age, they don't look when they back their cars out of driveways anymore. It's like "'Well, I'm old. I survived, let's see if you can!'"
It's difficult to tell whether George's parents are using this trope, or if they're just Jerkasses, but Jerry does seem surprised when his parents mention how horrible the Costanzas are because, "They're from your age group. I didn't know you could detect abnormal behavior among your own kind."
Fred Sanford of Sanford and Son. His constant threats of "the big one" (heart attack) and his "arthur-itis".
Merlin invokes this trope in his own show repeatedly, despite of not actually being a senior in this incarnation. Whenever he gets the chance to use his elderly magical disguise Emrys, he cheerfully insults everyone who gets in his way, especially Arthur and others who get on his nerves in his daily life. He also goes all out with his magic which he normally has to keep hidden, sometimes attacking enemies even when it's not strictly speaking necessary.
One example is when he's surrounded by a bunch of Knights, all of whom are close friends, but often like winding him up. So he knocks them all out and uses them as a staircase to climb onto his horse.
Jonathan: Now, mother, you can forget that crotchety old lady routine.
Mother Dexter: What routine? I am a crotchety old lady!
The hidden camera prank show Betty White's Off Their Rockers plays with this by having senior citizens often acting in rude or unpredictable ways, the question being whether people will react negatively or just let it ride because they're seniors.
The Doctor in Doctor Who pulls this relatively often. His first incarnation, which was the oldest-looking of all, was particularly fond of the trope. Since his later incarnations tend to look younger, he doesn't get away with it as often anymore. Ten summarizes it pretty well:
I'm the Doctor. I'm a Time Lord. I'm from the planet Gallifrey in the constellation of Kasterborous. I'm nine hundred and three years old. And I'm the man that's going to save your lives and all six billion people on the planet below. You got a problem with that?
In Matlock Ben has got this down to a fine art too.
Dowager Countess Violet of Downton Abbey snarks constantly. As she herself remarks, "I am beyond propriety."
The twitter account "Shit My Dad Says" that led to the books and newspaper columns of the author's father's grumbling.
Lampshaded in a Dilbert strip. An elderly woman, told that she has too many items for the express lane in a store, says, "It doesn't matter. I'm old and therefore you must do what I say." She then does everything possible to eat up time before falling into her handbag and being devoured by wolves.
A Calvin And Hobbes comic has Calvin questioning why old people slow down and become more complacent as they get older. In the end, he resolves that when he is old he'll be "going like a maniac." Hobbes immediately states that the world can't possibly wait for such a day, his voice (most likely) dripping with sarcasm.
Huey and Riley's Grandad from The Boondocks is an embodiment of this trope.
This is part of the reason why I'm Sorry I Haven't a Clue is able to get away with such filthy humour, thanks to the advanced age of its regulars. The rest of the reason is careful Obfuscating Stupidity leading to Innocent Innuendo. In particular, Humphrey Littleton had a persona of a grumpy curmudgeon who rather not be doing this rubbish, regarded the panel, the games and the audience as a nuisance and wasn't shy about saying so.
George Carlin's last special, It's Bad For Ya. He revels in being 70.
George Carlin: The first one is, you never have to carry anything heavy ever again. Everybody wants to help an old fuck. If you've got a big suitcase, or something like that, you know, you just kind of go like this a little bit... And you say "Yeah, can you help me with this?" They say "Yeah, hey, how far are you going?" "Indianapolis." Another nice thing about getting old is you can leave any social event early just by saying you're tired. Works great with family members. Just turn to the person next to you and you say "Gee, I'm getting tired, you know." "Oh, you're tired? Come on, grandpa's tired, grandpa's going to bed." And someone else says "But it's seven thirty in the morning!" There's always one asshole in the family. But the best thing about getting old is you're not responsible for remembering things anymore. Even important things; "But it was your daughter's funeral!" "I forgot!" You can even make believe you have Alzheimer's Disease. That's a lot of fun. You look around the dining room table and you say "Who are you people and where is my horse?" Then you stare at your eldest son and say "Agnes! I haven't seen you since First Communion!" You can even shit in your pants! They expect it! I haven't tried that yet, but I don't rule it out.
Jeff Foxworthy set a life goal of being a burden to his children and scaring his grandchildren.
Nick Swardson has a bit about him wanting to be old enough to shoplift and get away with it, along with speeding.
Nick: When I'm 90, I'm going to be going 90!
Ventriloquist Jeff Dunham has old man Walter. "Dumbass." In one special, Walter even ponders getting a job at Walmart now that he has retired.
George Burns: "I was always told to respect my elders. Now I'm at the age where, I don't have to respect anybody."
The computer game Knights of the Old Republic features Jolee Bindo, a Jedi knight who is at least sixty years old and probably quite a bit older. When asked questions about his past, he will deliberately launch into long, semi-relevant monologues. One of his best lines is "I'm old, dammit! I'm entitled to be enigmatic when I want to be!"
She is also a Sith Lady so hen lack of politeness is pretty understandable.
Cranky Kong from Donkey Kong Country. He's exactly as his name says in most of the games (aka always thinking of the good old days of the arcade), and actually sets off the events of Donkey Kong Land over a bet with King K Rool.
Wendy Oldbag from Ace Attorney is just like this. She rambles on and on about insignificant points, and gets pissed when anyone asks her to keep on track, and often calls poor Nick a "whippersnapper".
In 8-Bit Theater, Black Mage's brief career as a cobbler was haunted by an old woman who made inane demands because she was "old and quite possibly senile." Possibly one of the few murders of his the audience will see as justified, if only somewhat.
Another one that could fall under this trope is the old man who lived in Radio Castle. He was rude and never stopped complaining about how things used to be better in the old days because you could be openly racist and there weren't any gays. The guy seriously never stopped complaining. Black Mage ended up pushing him out of an airlock.
Cotton Hill in King of the Hill takes this trope to sociopathic levels. Although, he was probably always a Jerk Ass regardless of age. He does use his age and his status as a veteran to attempt to get away with being a maniac, though. Whenever anybody attempts to call him out on acting like a psychopath, he usually responds with, "I'm old! I gots no shins!"
Professor Hubert Farnsworth from Futurama even has a "crochety grandpa discount card" (which expired, despite being good for a lifetime), and once uttered the line "Now, if you'll excuse me, I have to go buy a single piece of fruit with a coupon...and then return it, making everyone wait in line behind me while I complain!"
In the card's defense, Farnsworth has been declared dead at least once.
Professor: You take one nap in a ditch in the park and they start declaring you this and that!
Col. Stinkmeaner from The Boondocks is explicitly stated as having been a Jerk Ass at every point in his life, but when we see him he is quite old.
The Critic Jay's father Franklin acted insane almost constantly. His wife used the "He had a stroke" excuse. Once admitting immediately that he hadn't really and they just said that to explain it.
This wasn't because Franklin was elderly, though; the man was insane. A brief glimpse into his mind revealed he drove like a maniacal Jerkass because he was dodging Donkey Kong's hurled barrels with the car horn as the jump button.
The old people in the South Park episode "Grey Dawn" who want to drive, despite being mentally slow and having no regard for the safety of anyone else on the road... or on the sidewalk... or in buildings... or... Well, you get the idea. This was inspired by a nasty Real Lifeaccident.
Ratchet from Transformers Animated. There was even a subplot of an episode dedicated to Sari and Bumblebee trying to teach him to be less abrasive. Needless to say, it failed miserably!
Grandpa Wolfe from Rocko's Modern Life: He definitely hates Wallabies & Kangaroos and he acts hostilly towards Rocko. Even with Grandpa Wolfe's incredibly poor eyesight, Rocko still wasn't safe.
On Adventure Time Marceline the Vampire Queen tries to invoke this (singing "I'm not mean, I'm a thousand years old, / And I just lost track of my moral code"), but since she doesn't look or act like an old person, no one really buys this excuse.
There's a joke floating around the internet which invokes this. An old man is attempting to park his car, but is cut off by a smart-ass teenager, who then shouts, "Sorry, but that's what happens when you're young and fast. The old man, nonplussed, simply backs up, hits the gas, and smashes his car into the back of the young man's. He then turns and says, "Sorry, that's what happens when you're old and insured."
Walter, one of comedian Jeff Dunham's characters, is this trope in ventriloquist puppet form, played for laughs. He's actually one of the more popular ones, mostly because everyone knows someone like that.
Used in one of Patton Oswalt's comedy bits about how old people should have one law a year no longer apply to them, but partially subverted due to caveats:
"When you turn one hundred...you can legally commit murder. You can murder anyone. You cannot shoot them, stab them, or poison them - anyone you can strangle, or pummel to death with your bare hands is fair game. ...How many of you would help if someone called, 'Help! A one-hundred-year-old woman is strangling me!'"
Nick Swardson's first "Comedy Central Presents" act included a routine about this. He mentions how when he's an old man, he will steal things 24/7, and if caught by police, would only say "I'm old", and how he would always break the speed limit, and if the cops stopped him, would say "I'm dying". He also jokes how he would curse at his grandchildren, and listen to gansta rap.
Betty White. Just watch a recent interview and you'll notice that she makes all sorts of snarky remarks and justify it by saying "I'm 88 years old. What do I care?" It's the main reason her younger fans love her!
Certain forms of senile dementia, by causing the frontal lobe to go before the rest, result in this as the sufferer slowly loses their social skills.
Then again, once you've been around for long enough, you sometimes just no longer give a fuck.
While Wanda Sykes is not a senior, the above mindset is exactly what she finds herself adopting the older she gets. Which apparently led to some problems at the grocery store when she responded as such to a bagger who was "sixty-three years old, and she didn't give a fuck either!"
Old people can generally get away with racism and blatant rudeness since few people are going to say or do much.
In fact, in many cultures, it's considered inappropriate to say anything back since elders are supposed to be respected unconditionally.
Japan's hierarchical culture requires junior members of a group to show deference and respect to their seniors, but there is no obligation on the seniors to show any respect to the people under them. Even in relationships where the senior isn't deliberately obnoxious to his/her subordinates, this can still be quite evident in conversation, with the senior's side conducted using casual language whilst the junior is expected to remain polite and formal. If the senior really is a jerk, then the junior has very little recourse as it's considered bad form to complain about being berated or abused by a senior.
China's even worse than Japan. It's a Confucian idea that goes back to respecting your superiors above all else (coupled with the part about "always save face unless you want to shame your entire family then, now, and forever").
Korea is also a Confucian society. Elderly people will often push and even elbow their way through crowds with no complaints from the younger generation (at least not verbally). They are usually very shocked when they do the same thing to a Westerner, and the Westerner snaps at them or even pushes back (especially likely if said Westerner is American, due to Americans' love of personal space).