Most of the characters in 1/0 at some point, but Zadok constantly.
Adventurers! has one in each camp: Ardam for the heroes and Argent for the villains. Though Ardam is usually more "exasperated" than "deadpan".
Both Paige and Norah from Agents of the Realm seem to have it as their primary defense against the mess they are plunged into. The former uses it to be a voice of reason for the cast, while the latter employs it against the bleeds as much as her sword.
Erfworld gives us Prince Tramennis and, to a lesser extent, Foolamancer Jack Snipe. Justified in Jack's case. He's a Foolamancer. It's his job to see the world as it is so that he can manipulate it. Prince Tramennis is just balancing out the rest of his family.
Every main and supporting character in both Michael Poe's Errant Story have their moments of this, but the males seem especially prone to it. Jon and Ellis probably have a Snark/Strip ratio of 2:1.
Harold Eastwood:(on Virus smoking in his intro page) You mean it was a lame attempt to look badass. Syrus "The Virus" Zuviel: Did it work? Eastwood: No, you just looked like a regular ass. Virus: Ha. And indeed, ha. Don't quit your day job Harry.
Most of the cast of Fletcher Apts except for Kia and Mr.Fletcher.
Daniel from Footloose, which can result in his receiving a smack (or boot) upside the head from his twin sister Jin.
The man: Don't try to stop me! *runs off to confront Edith. The girl (grinning): Oh, no. Don't.
Said partner doesn't stay far behind.
The man: Tch-what's this blade made of? Edith: B*** deterrent. The man: Cute.
Guilded Age: Gravedust, paradoxically. He's almost completely lacking in humor, so on the rare occasions when he does crack wise, he does it with such a straight face that it's hard to tell whether he's actually joking or not. Case in point.
So, so, so many examples from Homestuck. Just within the main characters, Dave, Rose, and occasionally John all qualify, and beyond that, practically half the cast qualifies. There's a reason the verbal competition between Kanaya and Rose is measured by the "Flighty Broads and their Snarky Horseshit-o-Meter." And that said "Horseshit-o-Meter" explodes.
Rayne of Least I Could Do goes so far over the top with the Idiot Hero and Handsome Lech routines that most of the rest of the cast are divided into those who can use deadpan snarking to survive his bombastic ways (Issa and Noel), and those who turn into his punching bags (Jon and Mick). Noel is probably the best example.
Artax: She Who Must Not Be Named has taken That Which Man Was Not Meant To Know! Nodwick: Did she say where She Who went? Artax: To The Lands Which Know No Name! Nodwick: Uh-huh... let me know if we find any proper nouns in all this mess.
Lars from The Noordegraaf Files. His first four lines are pure unrefined sarcasm. Akila, when she's in the "Tsun" half of her Tsundere personality.
Crystal: Arrgh! You little twit, I'm gonna kill you! Belkar: Yeah, and I'm going to drop a house on you and sing about how I represent the Lollipop Guild. C'mon, let's keep our threats realistic, shall we?
Redcloak: I'm on my way to finish zombifying the monsters we killed up in the tower. MitD: Yeah, I can help with that. Redcloak: Really? So, I guess those three boxes of mallomars you finished off somehow earned you enough XP to gain 5 levels in cleric overnight. MitD: Well, they were especially chewy.... Redcloak: Then unless you are volunteering your services as raw materials, I don't think you are going to be much help.
Captain:(in front of a computer with a destroyed monitor) Hello computer... I'd like one free internet please. Maybe if I twiddle these wires... Mr. Snippy: You are an idiot. Captain: What? No... Why? Mr. Snippy:(holding up a cell phone with a destroyed screen) To illustrate, I shall take a photo of your epic failure with my phone.
Mikkel tends to be this, if he's not outright being The Gadfly. He'll do things such as explaning to Reynir that the bruise he got from a Plague Zombie will not make him catch The Plague because it didn't actually break the skin, unless he happenes to have licked the the bruised arm right after it happened. He then actually makes sure Reynir didn't lick his arm just to be safe, despite the fact that due to The Plague being partially airborne, Reynir has been wearing a mask protecting his nose and mouth since before he got bruised and hasn't taken it off yet.
In the prologue, Mikkel's great-grandmother knows how to deal with a passenger demanding an entire ferry to go against newly implemented travel restrictions so he can get to a work meeting on time:
Signe: Oh no, an important meeting? I'll call the captain right away on our direct emergency line! [picks up imaginary phone] Hello Captain! Oh yes I'm fine, how are you? So hey, I have a passenger here who would like you to turn back to Ystad...Oh? Oh dear, how unfortunate. I'm sure he'll understand, he seems like a reasonable man. [mimes hanging up] I'm sorry, another passenger already asked to be taken to the Bahamas, so we're heading there now. But you're next in line with your request!
Ruby, in Sticky Dilly Buns, has a bumpy start as a snarker, being too neurotic to manage the deadpan well and living in a fairly snark-light comic. However, by this strip it seems that she's beginning to develop the skill. The male disguise may help her relax enough, but mostly it's the golden opportunities that she's offered; the comic may turn out to be about the creation of a competent snarker.
Cassie, Chris and Alan are all snarkers in Sunstone.
Also many people in another of the author's comics, Super Stupor. Come to think of it, perhaps every character R. K. Milholland creates. And thus, probably Milholland himself, as well.
Liam: Nope. I just come here for the books on vinyl.
Bert and Darby from TRU-Life Adventures are the most consistently snarky among the toy store staff, but almost everyone working there gets a moment. It must be a survival technique for dealing with the customers.