Both Prince John and his actual snake servant, Sir Hiss (the main page illustration) from Robin Hood are prime examples of this trope.
Kaa from Disney's The Jungle Bookis a Smug Snake. This is the complete opposite of his personality in Rudyard Kipling's original book, where he was more of an Old Master who has the respect (and fear) of the Jungle.
The Smug Snake in the book: Shere Khan.
Gladstone Gander in the DuckTales cartoon. See the comics section.
Though Gladstone's Smug Snake characteristics were notably more subdued in his animated incarnation than in the original comic books. The episode "Dime Enough For Luck" even goes so far as to portray him in a fairly sympathetic light.
Jafar. He thinks he is very clever, and does manipulate the heroes quite a bit, but in the end his lust for power prevents him from thinking through the consequences of his actions, specifically that being a genie would force him to live in a lamp and grant wishes, which proves to be his undoing. He even has a bit of a snake theme going on. Unlike most of these smug snakes, Jafar graduated to a Magnificent Bastard in the second movie.
From Transformers, Starscream in almostall ofhis incarnations. In G1 he fancied himself the smartest, most cunning and handsomest Decepticon. When he wasn't complaining to Megatron about how he would've defeated the Autobots eons ago, he was openly plotting ways to top the slag-maker. All of his schemes failed miserably with at least one or two nearly destroying the earth. He was far more interested in becoming the Decepticon leader than leading them effectively in the rare moments when Megatron was out of the way. His Transformers Animated incarnation behaves similarly in this regard, but is physically dangerous enough to back himself up, whilst his Movieverse and Transformers Prime incarnations are tired of Megatron's leadership and genuinely believe they would make better leaders, but are unable to oppose him directly.
Prince Charming, in Shrek the Third, manipulates the other villains telling them that if they join him, they will all get their "happily ever afters" when all he really wanted was for them to help him get what he wanted, which was the throne for himself.
Also Lord Farquaad in the first movie and Rumpelstiltskin in the fourth.
The Monarch would be this if he wasn't actually a capable threat who merely devotes himself to annoying Venture. Frankly, every villain on The Venture Bros. fits this trope, with the possible exception of the ones who don't have enough self esteem for the "smug" part, and maybe the Sovereign, who usually appears to have enough on the ball to qualify as a Magnificent Bastard.
The nudist aliens from the Futurama movie Bender's Big Score. You'd think that scamming the entire Earth and forcing its population to the outskirts of the solar system would make them Magnificent Bastards, but no. Maybe if they didn't do everything, everything, in the most profoundly annoying way possible (and also if they didn't look the way they do, eeuuuugh). But that's spammers for you.
Both Sterling and Malory Archer fall under this category.
Slade from Teen Titans. He's a creepy guy, but his manipulations leave a lot to be desired (such as telling Robin that he enjoyed fighting his friends.) It's mostly because he can't understand or control the heroes as much as he'd like to. And the fact that he's widely perceived to be a pedophile doesn't help. He has his moments of magnificence though, especially after becoming Trigon's henchman.
Unlike some other Smug Snakes, Slade does learn from his mistakes. After getting his butt kicked by the whole team, he makes sure that he never winds up fighting them all at once again (at least until he gets superpowers of his own) and after his manipulations of Robin failed because they hinged only on their being Not So Different, he systematically deconstructed the mind of his next apprentice, Terra (and turns her into a person puppet without her knowledge if that fails). Unfortunately, he's never able to lose the old Villain Ball (sometimes being a sadistic sociopath is a problem), and therefore never crawls out of full Smug Snakehood, though he does get better towards the end (see his Crowning Moment of Awesome against Trigon's demon warrior.)
Other Teen Titans main villains, such as Brother Blood from Season 3 and The Brain from Season 5, also count. Both are very threatening, but their inflated egos prove to be their undoing in the end.
The Sequel SeriesThe Legend of Korra has Tarrlok. He's certainly clever, and turns out to be a formidable waterbender (even without his secret bloodbending ability), but he's too over-confident that people will do what he wants, and reacts badly when people refuse to be cowed. This is best exemplified by his reaction to Korra flatly refusing to give in to his blackmail, calling out his mismanagement of the public relations crisis, and comparing him to Amon; he attacks her, which is not only politically unwise (since attacking the Avatar will lose him a lot of support), but also allows Korra (who is an excellent fighter, hates him already, and is known to have an explosive temper) to fight back. Considering the look on Korra's face◊ by the end of it, he could have been in a lot of trouble without his secret ability to bloodbend.
And just to hammer the point home, the kids even got Genre Savvy about his smugness. One episode had Lucas, Nick and Jessica mess up his plan by simply pointing out how painfully obvious it was, which caused him to lose his head and attack.
The Almighty Tallest Red and Purple of Invader Zim. Being, well, the tallest of the Irken people, they're both very smug and full of themselves. Unfortunately for their credibility, the only reason Zim is "invading" Earth is because their attempt to get rid of him backfired.
Looney Tunes mainstay Wile E. Coyote had a handful of cartoons where he faced off against Bugs Bunny, and not only talked but took to smugness like a fish to water. His outlook on life is best summed up by his speech to Bugs in their first outing together, "Operation: Rabbit".
Wile E.::Allow me to introduce myself. My name is Wile E. Coyote, genius. I am not selling anything nor am I working my way through college, so let's get down to basics: You are a rabbit and I am going to eat you for supper. Now don't try to get away, I am more muscular, more cunning, faster and larger than you are, and I am a genius, while you could hardly pass the entrance examinations to kindergarten, so I'll give you the customary two minutes to say your prayers.
This trope is really driven home in the final exchange of the episode, which functions as an excellent set of Book Ends with Wile E's original speech:
Wile E.: Allow me to introduce myself. My name is Mud!
Daffy Duck often leaned as this in his later antagonistic bouts with Bugs. While he is manipulative to decieve Elmer, to the point of making him his borderline subbordinate, he wastes all his effort trying to send him against his much more cunning rival, who always manages to send things firing back onto him. This is taken Up to Eleven in his bouts with Speedy Gonzales, where he is incensed enough by the rodent to try and do the dirty work himself. And within The Looney Tunes Show, this would pretty much be set in stone if not for his Character Development.
Alluro in Thundercats is so smug, he'll lounge on his enemies' tank waiting for them to return, and his actual method of combat is to attempt to psyche them out into thinking they can't possibly win against him. As he's taller, broader-shouldered, and more muscular than any other cast member, he could probably handle himself quite well in a fight, but he never actually gets physically involved, and so his psyche-out attempts always wind up backfiring.
Seen in an RAF Cold War instructional film warning of the dangers of HISS (Hostile Intelligence ServiceS) represented by a smug cartoon snake with a Fake Russian accent. All his dupes were naturally caught by the vigilant RAF police, but the evil HISS would just go on to the next victim.
Gibbs of Titan Maximum, despite being both Dangerously Genre Savvy and the Only Sane Man is this due to his incredibly smug nature and the fact that his victories are invalidated by the fact that his opposition is a team of incompetent jackasses, thus mostly succeeding more out of their own failures than anything else.
Troy from Titan Maximum might also count. "T-R-O-Y! Why? Because I rock!"
Mr. Burns sometimes takes Smug Snake to a ridiculous extreme. For example, one episode involved a plan on Burns' part to block sunlight from reaching Springfield, and a town hall meeting was held about it. During the meeting, the town was being shown what Burns' oil drilling operation did to Bart's pet dog, who was shown needing to use wheels just to walk down the hallway. Burns walks in at exactly this moment, and, with a big smirk on his face, says this:
Burns: Oh, those wheels are squeaking a bit. Perhaps I could sell him a little oil.
However he met his downfall at the fact he was too impulsive. As he later admits in the second of the two parter, nobody could touch him so he felt like he could do anything. He spots Maggie holding a lollipop and decided to act something he wanted to do earlier; steal candy from a baby. During the struggle, the gun he was holding slip out of his holster and into Maggie's hand, going off and shooting Burns.
Sideshow Bob. He is educated and indeed clearly a mastermind. But Bob is such a showman that more often then not, his schemes fail because he either misses a small clue or just loves to be theatrical in his work. To be fair, a lot of these small clues are easily missed. For the most part, Bob has very clever schemes; it is more often a matter of circumstance that they tend to fall apart. He does show some signs of being a Smug Snake , but is a very ambiguous example, and most definitely less of an example than Burns.
Blaineley from Total Drama World Tour has a very inflated image of herself but isn't in the same league as Heather or Alejandro when it comes to manipulation and ruthlessness.
Justin from the previous season also qualifies. He boasts about being a great, manipulative strategist but it turns out that he's The Brainless Beauty whose manipulations rely solely on his good looks. When his face gets damaged, he barely poses a threat.
In ChalkZone, Reggie Bullnerd is very clearly stupid, but thinks he's smarter than he is anyway.
In the Fast Forward Season of Teenage Mutant Ninja Turtles 2003, we get Darius Dunn, a Manipulative Bastard and a master of deception who is surprisingly so arrogant that he berates his goons whenever they fail him, and doesn't take well to the Inuwashi Gunjin no longer willing to serve him, nor does he take well to the firewall set up by Cody to keep information about his time window a secret from everybody. He even throws a hissy fit when he finally loses his control over the Gunjin themselves.
In the Ultimate Spider-Man animated series, The Wizard is cocky and arrogant in both fights against Spider-Man, but he loses his cool when Spidey turns the table on the Frightful Four, especially in the second fight, where his team loses the numbers advantage.
Sym-Bionic Titan: Baron, the Draco Malfoy-esque kid Lance conflicts with at the boarding school he attended as a child. Before fleeing Galaluna, the Commander the actual traitor who accuses him of murdering Galalunians is also this.
In Robot and Monster, Robots older brother Gart who always rub it into Robots face that he is better than him, and makes sure everyone knows how good he is.
Grodd in Justice League. It's very unlikely that most villains would make a speech to an all-human crowd where he claimed "Humans are slow, ugly, immoral, and have an unpleasant body odor!" unless they were Brainwashed and under his control, like in this case, but then, that would sort of defeat the purpose of making such a speech at all. He was doing it to feed his already-inflated ego.