Batman: Jim will pull through! Alfred: Or what, master Bruce? You'll dress up like a giant bat and haunt the night for the rest of your life?
Whenever Batman (in any incarnation) isn't either moping around in Wangst or being The Comically Serious, he's generally the one with a deadpan line. Or, as Jaime Reyes (Blue Beetle III) put it, "Batman's actually kind of funny, in a dry, scary way." Typically, Batman needs Superman as a foil if he's going to be funny.
The Robins (most of them) tend to pick up the slack as far as snark goes.
Captain Klutz, of all people, gets in a good one to a movie star in "Hollywood Whodunit," even though he's supposed to be dumber than dirt:
Deanna Drano: My life is in danger! Klutz: I saw your last picture and I'm not surprised! I narrow it down to two suspects! Your critics or your audience!
Everyone says lines like that in any book involving Deadpool.
Much of the cast of Death Vigil, but extra points to Sam and Marlene.
Eva Kant from Diabolik has her moments. Her favourite snark is insisting her husband's death (devoured by a panther) was an accident, as he was trying to set the panther on her, and Eva didn't mean to set the panther on him.
Doctor Strange on occasion. His manservant Wong is pretty good at it too. Same goes to Umar, especially towards her brother, Dormammu.
Flash Forward/Negative Man II of the Doom Patrol. His nickname is an in-joke referencing the fact that there was a "Negative Man" in the original Doom Patrol — that, and the fact that he's extremely hard to get along with due to his icy personality and seeming inability to say anything nice about anyone.
A newspaper comic example: When Garfield began, Jon Arbuckle was the original snarker (being most notorious during the fall of 1978), with Dr. Liz Wilson taking that role when she was introduced the following year. (Jon at the turn of the eighties was not yet the Straw Loser he is today). Finally, by the mid-1990's the cast had been reduced to Garfield, Jon and Odie (apart from the unseen Ellen and Jon's various blind dates), and the fat cat took the deadpan persona he is today.
John Constantine the Hellblazer embodies this trope. Not only is he a witty talker, he speaks it with his English accent, which makes it twice more badass.
Hellboy often uses deadpan. His Catch Phrase "Ah, Crap," can be said to be an example, as is his habit of yelling "Boom!" when he punches someone with the Right Hand of Doom.
Black Bolt from the Marvel ComicsThe Inhumans is The Voiceless; if he were but to whisper, it would unleash a shockwave strong enough to destroy a city. Despite this, he's constantly thinking such lines. During his time with the Illuminati, fellow member Charles Xavier doubles as a translator. Also, when he wants to declare war, well, he doesn't beat around the bush: he declares "War."
The Illuminati miniseries has a very funny part where Black Bolt comments that his wife (who speaks for him) never lets him get in a word edgewise.
Elaine Belloc from Lucifer has occasional moments of deadpan snarking, most notably when she sat at the table with Archangel Michael, Lucifer and Destiny of the Endless debating heatedly. Her comment was: "Another glass of testosterone, anyone?"
Atticus Pix from Ministry.
Matt Fraction's 26 issue run on Punisher War Journal gave Frank a sort of dark, subtle sense of humor.
Punisher: Nobody gets me. Maybe it's the skull.
Denny O'Neil and Greg Rucka's versions of The Question, although as Vic Sage he tends to combine this with Jerk Ass.
According to the Author's Notes, this was deliberate in regards to Renee Montoya in 52. When she's out of the mask she's serious, angtsty and often quite brusque, when she's The Question, she starts to snark and make jokes. Not well, but it shows how she can become someone else.
Sonic is incredibly snarky in his comic series. During one battle with the near omnipotent Enerjak, Sonic makes several puns on the name. When Enerjak immobilizes him with chaos energy and asks if he's quite finished with the witty remarks, Sonic makes seven or eight more cracks in rapid succession, before Enerjak hurls him through a wall.
Spider-Man, to the point of deserving to have the trope named after him. Though really, he spends a lot of time in incredibly-energetic-snarker mode too. At one point, this embodied him so much, a lot of people used to call them "Spider-zingers".
Played with by Spider-Man 2099, who's terse and straightforward in costume, but a killer snarker in his civvies.
His snarkiness is well known even in-universe. In an issue of Excalibur, the members of the Wrecking Crew briefly mentioned Spider-Man's name, elliciting a "I hate Spider-Man" from one of the members. The response: "Everyone hates Spider-Man."
In the Secret War miniseries, Spidey met Black Widow out of costume and made a quick joke. Widow suddenly realized who she was speaking with.
Gryph:(upon being levitated by Zayne) I seem to have lost weight. (reading the news report on Zayne's escape:) Gryph: "... Failed Padawan..." "... Slew classmates..." "Fugitive is armed and..." Umm... Zayne: Dangerous? Gryph: No. "Deranged." Well, that certainly sounds like you.
The bulk of the characters in Star Wars: Rebellion volume 2: The Ahakista Gambit have one or two smart remarks, but Baco Par, the Snarky Non Human Side Kick is notable in that he barely has ten lines which aren't snarky. See the quotes page.
In contrast to Spidey, Clark Kent tends to be quite snarky at the Planet, but drops it as Superman. This is Depending on the Writer — in the Movie, Superman was at least as snarky as Spider-Man ever was.
It often depends who he's talking to, as well. When he's "Superman", say in public, or against a villain, no snarking. When he's around somebody that knows the real him (Clark), like Batman, he tends to be more snarky.
In the New 52, he's actually fairly witty or sarcastic with most of his lines, both as Superman and Clark Kent. Like this particular gem, in a spaceship, with a gaping whole blown in the side of it by a giant:
Superman: Grifter, take your friend hiding in the rafters-
Superman: Seriously? Never mind, just let me handle this-
Terra, from Teen Titans, is iconically sarcastic, which hints at her infamous twist. Her second version, and cartoon version, lack this sarcasm.
Wilq the Superhero, the main protagonist of a Polish comic series of the same name, is so sarcastic that he was actually called "the most frustrated character of Polish comic books" by the Wprost magazine.
X-Men: Gambit (to name just one) is the absolute King of this trope. Every other sentence that comes out of his mouth is a snark. And you can never tell when he means it...
Suprisingly, Cyclops is quite snarky when he wants to be as well. In the First Class comic for example:
Cable has his moments too. Such as during the X-Cutioner's Song crossover, when informing Wolverine and Bishop that he'll need to make adjustments to his space station's teleporter if they want to bodyslide to the moon.
Wolverine: How long will that take? Cable: If I do it myself, about twenty, twenty-five minutes. Wolverine: And if we help? Cable: An hour and a half.
X-23 has a very subtle and generally black sense of humor, and when she does make a joke it's generally this. With a particular emphasis on the "deadpan."
Dr. Nemesis has a particularly scathing and sharp tongue, once telling Emma Frost he would personally destroy every fetishwear store on the planet if she doesn't follow his orders.
To be honest, it would probably be quicker to name an X-Man who's not this trope.
Every single member of the Young Avengers displays this to some extent. They beat up about one enemy for every ten lines of snarky dialogue and Witty Banter.
While he doesn't display it very often (mainly because he doesn't talk much at all), the Punisher has been shown to have a very dark and dry sense of humor sometimes.
Cop: "Any time you want to finish this, big man, I'm ready. You and me, one on one-" Frank: "I'm not really dating anyone right now."
In another story, Frank had allowed himself to be arrested and imprisoned in order to get at some incarcerated wiseguys. While he was being led to his cell, the corrupt chief guard pointed out a heavily muscled inmate who was giving Frank a death glare. "See that guy, Castle? He's the toughest con in here and he's the one they're going to send after you." The Punisher promptly breaks loose, overpowers both guards, grabs a baton and uses it to beat the inmate to death before anyone could stop him. Tossing the baton aside, he looked at the chief guard. "Tell them to send the second toughest."
In any comic book written by Peter David, the majority of the cast will be snarkers.