As the characters of Hayate the Combat Butlerknow that they are in fact characters in a manga/anime it typically results in literally almost every character being sarcastic or witty if they have any lines at all. Nagi and Hinagiku tend towards snarking at villains and some of the more ridiculous weirdos that pop up, but the Student Council Rangers, Ayumu, Wataru, and even Maria all make remarks at the expense of the plot or craziness around them. Hayate himself probably takes the cake, especially in the manga where he is a lot more cynical than he usually appears and has had exasperated reactions to just about everything and everybody. The series is so full of snark that when Hayate and Hinagiku are inadvertently acting like a lovey-dovey couple with no other characters around it resorts to using nameless background characters, a pigeon, and even a potted plant to make sarcastic comments about them.
YuYu Hakusho especially in the English dub, with the somewhat simplistic dialogue replaced with witty and sarcastic comments/insults. Especially Hiei and Yusuke, but also Kurama, Genkai, Shizuru, Kaito, Koenma, Jorge Saotome, Koto (when the idiocy around her gets too much, especially towards Chu and Jorge), Shishiwakamaru (in the final season, at least), Sniper, Atsuko, Toya (when he's not being stoic), hell even Kuwabara shows this very rarely. The snark doesn't stop with the heroes and their supporters. Some of the major villains such as Sensui and Sakyo had their moments.
Every single word in Rat Queens drips with sarcasm. And most of the spaces between words, too.
Pick an MST fic. AnyMST fic. Considering the genre is made on mocking bad fanfics and pointing out inconsistances, it's a crime not to have it full of Deadpan Snarkers.
The Wizard in the Shadows has literally everyone snarking at one point or another, usually to deal with how completely weird their lives are and the darkness of the times.
The Infinite Loops take place in a multiverse of snark, mostly due to every reality being trapped in a time loop and those that are aware of it have to either accept that fact or potentially go insane.
Tony: You walked right into this one. I dated hotter chicks than you. Brandt: That all you got? A cheap trick and a cheesy one-liner? Tony: Sweetheart, that could be the name of my autobiography.
Batman Returns. In a film as nihilistic as this one is that should come as no surprise. While the Penguin, Selena Kyle, and Alfred lead the pack in pure snarkiness, nearly every character from the Mayor on down have a snark moment (except Commissioner Gordon who has maybe five short lines of dialogue in this outing).
Percy Jackson. The powers that demigods and gods are born with must include snarkiness, because well, they are. Even the chapter titles are snarky!
The Nightside series is chock full of snarkers, as it's set in what's probably the most jaded place on Earth.
Harry Potter. There's Snape, McGonagall and Phineas Nigellus for starters. Much of the humour, especially in the later books, comes from the characters snarking at each other. In the core trio of Ron, Hermione and Harry, snark is passed around like a hot potato. Fred and George, as the series's two most blatant sources of Plucky Comic Relief, deserve special mention.
Frequent in The Dresden Files since the main character is a massive Deadpan Snarker and almost every other character has at least a few snarky moments. Even Michael gets a moment or two, particularly when borrowing Harry's name for the Denarians. Harry claims that the Dresdenverse runs so strongly on this that badass immortals will be insulted if he doesn't snark at them, implying they're beneath his snarking. Take that with a bit of salt, because he was justifying mouthing off to two incredibly-dangerous beings to one of their lower-ranked (but still badass) coworkers.
Scott Lynch's Gentleman Bastard, where the lead character is a snarker, his trusted associate is a snarker, the rest of their team full of snarkers, their allies, enemies and targets are snarkers. The flashbacks show that the past times also were full of snark, whether it is in Camorr or among Bondsmagi. Locke Lamora seems to be physically incapable not to snark, even if doing so would save him a world of pain - which may be why he is the main character.
Live Action TV
Mash. Even the blatant idiots get off a few good wisecracks, just not as many as Hawkeye and company. Hawkeye is a great example of Stepford Snarker who is really messed up but uses humour and sarcasm as his defense mechanism.
The main cast of the first four Star Trek series qualify, in a relatively restrained way, adding more to the "high-class" image of Starfleet and Trek humans than anything else.
Scrubs. Janitor, Cox, Jordan, Kelso, Carla, JD... List goes on and on. Everybody is sarcastic with everybody.
My Family: Husband and wife Ben and Susan seem to be engaged in a constant deadpan snarkery contest. Easy to see where their son Michael gets it from.
House: We have a protagonist who practically cannot exhale without snarking, we have his team who eventually learn to snark back at him (enabling 2-4 player snarkball ping pong matches), we have his best friend who normally is unsnarky but at times cannot resist it, we have his boss who breathes sarcasm (possibly as a reaction to the snarking protagonist)...
Red Dwarf: Lister and Rimmer's interaction in early episodes consisted solely of Snark-to-Snark Combat. The ship's computer Holly (his male form) hardly opened his mouth without being ironic or sarcastic. Cat is the group's dumbass but he had his snarky moments as well. Holly in a female form alternated between The Ditz and a solid snarker. When they got android Kryten, he was quite servile and literal-minded, but Lister managed to break his programming. In his "lie mode", he could snark gloriously.
Veronica Mars. It's easier to list who isn't a Deadpan Snarker, and the only main character on that list is a dog. The rest of the list is two minor recurring characters.
Firefly: The whole intrepid crew are Deadpan Snarkers, especially Mal (The Captain and The Hero), Zoe (his Lancer) and her husband of an Ace Pilot Wash. Jayne, a hired gun and their tough guy, is the group's Ditz. Kaylee The Chick was generally too nice to snark, but when she was angry, she could do it. (Inara: "So are there aliens among us?"— Kaylee: "Yes, and one of them is a doctor." She said it when Simon kind of insulted her, albeit not intentionally.) It's safe to say that everybody from the main cast had some smart-ass comments.
Maria Hill: What does S.H.I.E.L.D. stand for, Agent Ward? Grant Ward: Strategic Homeland Intervention, Enforcement and Logistics Division. Maria Hill: And what does that mean to you? Grant Ward: It means someone really wanted our initials to spell out "shield."
Hogan's Heroes. The only main characters who don't get to snark at least Once an Episode are Carter and Schultz, and even they get their chance at snark sometimes. Even AdolfverdammtHitler gets an amusing snark in. When Hogan, as part of The Plan, pretends to want to spread German propaganda, he spreads it in a way that gives a Naziism-is-stupid impression. Hitler himself calls the studio to tell Klink that if Hogan tries to escape, to let him.
Gilmore Girls: Everybody snarks in the quirky town of Stars Hollow, though some of its Cloudcuckoolander inhabitants sometimes serve as The Ditzes and dumbasses. The Proud Elite represented by Emily and Richard Gilmore and posh Chilton and Yale students are snarky a lot as well. Rory and Lorelai trade snarks with each other in most of their dialogues, and they both love arguing affectionately with Luke (an owner of the local bistro and Lorelai's Will They or Won't They? love interest) or Sookie (Lorelai's Heterosexual Life Partner). Luke and his nephew Jess have Snark-to-Snark Combat dynamics. Well, the list could go on and on.
The cast of Blackadder changes every season, but it tends to be divided almost evenly between the snarkers (Blackadder, Melchett, and so on) and the people who are too dim to notice when they're being snarked at (such as Baldrick, George, Baldrick, Queen Elizabeth, and Baldrick). Did we mention Baldrick?
The Middleman is an interesting example, as the title character himself is too earnest to be particularly snarky. Everyone else, on the other hand...
Blake's 7, set in a Crapsack World where snark is universal, having such uses as: distraction (anyone in need of a getaway; Vila); defence (anyone being held prisoner, tortured, shot at, etc; anyone dealing with Avon), coercion (snark-to-snark combat; Blake); everything (Avon). The more idealistic characters (Gan, Cally, Dayna, Blake) entered the series with a relatively low level of snark. Their snarkiness grew on a par with their cynicism, especially with Blake. Avon was King of Snark, and every character becomes more snarky proportionally to how often they interact with him. Except Dayna, who can out-snark him from her first episode.
LOST: Snark is basically how everybody communicates in this show. If you look it up, nearly every Wham Line is snark.
Doctor Who: The main character snarks on a semi regular basis, and when he isn't doing it, he gets snarked at. Three, Nine, and Ten are among the snarkier Doctors, while Tegan, Turlough, Captain Jack, and Donna are among the snarkier companions. Is especially prevalent in the Eleventh Doctor's era. He and the Pond family basically communicate only in snark. Clara Oswald and the Doctor snarking it off is also a sight to behold. This tumblr is a collection of gifs of snappy putdowns from the whole series, Classic and revival. There are an awful lot.
Basically everyone in Frasier. In their defense, they have to be this way: anyone who can't hold their own in a snark-off would get eviscerated by the Crane brothers, who are probably the deadpan world champions.
Elementary. Sherlock's lack of tact and often bizarre leaps of logic tends to elicit sarcastic responses from Joan, Captain Gregson, and Detective Bell.
Sherlock: Have you always been this observant? I'm asking sincerely, I'm wondering if exposure to my methods has helped you in anyway.
Bell: [sarcastically] Actually, before you came along, I've never closed a case. Neither had the rest of the department. Most of us were thinking of packing up, leaving. Letting the city fend for itself!
The X-Files, starting with both protagonists Agents Mulder and Scully and their boss AD Skinner. Episodes with snarky astrologers like Madame Zirinka from "Syzygy" or snarky cynical psychics like Mr Clyde Bruckman belong among the most memorable.
Stargate SG-1 and Stargate Atlantis have the entire cast snarking it up, some more deadpan than others. Even The Stoic Teal'c gets in on it now and again, and with him less is more: it's epic when he does it. It's not just limited to the heroes either, with Ba'al and Todd the Wraith having a lot of fun engaging in Snark-to-Snark Combat against the people of Earth, often when they've been forced into an Enemy Mine situation.
Friends: Although Chandler is known as the Deadpan Snarker of the gang, the rest of the characters (apart from maybe Joey) would be extremely snarky on any other show. It's just hard to notice because 90% of his dialogue is snark, while everyone else only manages a weak 80%.
Yes, Minister, an Eighties BritishGovernment ProceduralsatirisingWhitehall. Jim Hacker, said minister, was often out-smarted by Sir Humphrey and managed to utter just a desperate snarky one-liner. His assistant Bernard was torn between being loyal to Minister and to Sir Humphrey, and he often snarked at both. Sir Humphrey was a master of elaborate sophisticated and sneering speeches. Jim Hacker's wife was a very nice lady, but could be snide with her husband as well, especially about politics.
Roseanne in spades, with Roseanne, Darlene, and in later seasons DJ pushing snarkiness to new heights.
Horatio Hornblower: There are many Deadpan Snarkers among the characters. Let us count the ways: Captain Keene, Captain Pellew, Midshipman (later Acting Lieutenant and Lieutenant) Archie Kennedy, the Duchess AKA Kitty Cobham, Gentleman Snarker Major Edrington, Tall, Dark and Snarky Lieutenant Bush, and some more. They do not exchange snarks with each other, but they are paired with poor Sarcasm-Blind Horatio, who is a genius at every other thing but irony, jokes and sarcasm usually escape him. However, some of Archie's smartass comments bring about his rare and most attractive smile.
It gets extreme in Dragon Age II, where everyone is sarcastic, regardless of whatever tropes they fit into. Even Aveline, Merrill and Fenris get in on the action occasionally. However, they are all overshadowed however by a Hawke with the Sarcastic Personality, who takes the prize as Kirkwall's resident goofball and Bunny-Ears Lawyer.
Mass Effect: Even the brightest Paragon Shepard is going to indulge in enough snark. Their crew members are usually worse! Taken into overdrive in the second and third games, where it seems to practically be a requirement for anyone wishing to join the Normandy.
Kasumi: Trapped in a Reaper. Could be worse. Don't know how. Beat I guess it could be full of rats.
Mix BioWare and Star Wars, and you get Knights of the Old Republic where it's possible to not only snark, but just barely fly under a PG-13 rating in doing so. The first game's crew snarks about as much as a Buffy marathon, with even Bastila and Juhani getting in the occasional zinger. Jolee and HK-47 are hard-locked in Sarcasm Mode. The second game resembles Blake's 7 with Atton aspiring to Avon's level. Kreia ought to register her words as a deadly weapon. Disciple and Handmaiden, by contrast, are too often oblivious to sarcasm.
Star Wars: The Old Republic, especially the Smuggler (who rides the line between Han Solo and Mal Reynolds of Firefly and the Sith Inquisitor (who is the Empire's answer to Blackadder, especially if played lightside)
No More Heroes: Travis may not be the only self aware character in the cast and a ton of people love making snarky remarks. The world itself is a massive self aware parody of videogame and anime conventions, just how subtle it is depends on the situation.
Homestuck. Even ditzier characters like John and Feferi have their moments of snark, and the snark levels go through the roof when Rose, Dave and Kanaya are involved.
In Shiniez more and more magnificent snarkers have appeared since the start of the second chapter and older characters have been seen holding their own against them in Snark-to-Snark Combat. ALL the many red headed characters in the strip save for Lisa are talented snarkers.
Roommates gave us this little gem to prove its standing:
Red vs. Blue is full of people who cope with their Crapsack World by snarking about it and each other. The full list of characters who don't snark at some point is pretty much Donut, who's too nice; Caboose, who's too stupid; and the Counselor, who's too creepy calm.
South Park, to the point where sarcasm itself is made fun of. "Sarcastaball" goes a step further and has Randy Marsh accidentally invent a sport by sarcastically suggesting it. Everyone involved with it in any way only speaks of it sarcastically, to the point that Randy temporarily loses his ability to speak of anything without sarcasm.
Hercules mostly by Hades, Meg, and Phil (and Cassandra in the series) mocking everything in sight.