The title character of Soul Eater starts out as this.
Yoh Asakura from Shaman King. He is THE Slacker hero. He is willing to work his ass off to become the Shaman King in the hopes of never having to do anything for all eternity. Also, he might be able to squeeze into stoner territory, from his name meaning leaf, a well known nickname for weed, to Viz and 4kids editing out the (much argued about) "Leaf" on all of his clothes.
Those Three Girls of Hayate the Combat Butler, Miki Hanabishi, Izumi Segawa, and Risa Asakaze, actually take this to the level of barely staying within the relevant plot of characters. Izumi is the only one who's actually shown interest in Hayate, Miki has actually disdained his interest and Risa hasn't seemed to decide whether she wants to be interested or not. All three love to hang out with Hard-Drinking Party Girl Yukiji, actually attempt to keep their grades barely above failing and only seem to show up often enough to cause trouble for the chapter to revolve around.
Ryner Lute from The Legend of the Legendary Heroes is totally like this. He's perfectly comfortable with going to prison because he won't have to do anything there. In fact, he considers it preferable to being in the military academy. He mostly does stuff only when Ferris threatens to kill him. He even made slacking into a philosophy: it's the motivated people who start wars and the like, and the unmotivated people get to suffer as a result.
Houtarou Oreki, the protagonist of Hyouka, claims he has no energy and lives his life in "the grey", the middle path between all forms of activity. His two rules he lives his life by are "One: Never do anything you don't have to. Two: If you have to do something, do it quickly."
Panda of Shirokuma Cafe is so lazy that he thinks working half of a half-day at the zoo is too much for him and blatantly tells Shirokuma in an interview for a job at Shirokuma's cafe that he had no intention of ever working. This attitude towards working has gotten him attacked with his mother's vacuum cleaner.
Hasabe in Servant × Service, so much so that the first questions he asked Ichimiya were details about break time and the whereabouts of places he could slack in. Whether he would develop into a Professional Slacker—it's a civil service job after all—is another question.
A rare slacker girl is found in Incandescence. The title character is an unmotivated young woman, barely attending college and mainly going to rock shows to her father's chagrin. Though as the trope suggests, she does start making steps to change her life.
Elixir from X-Men. Paired in an Odd Couple with Prodigy, who is an overachiever.
Scott Pilgrim - An unemployed 20 something who spends his time playing video games, hanging out, and playing in a band.
Wylie from 100 Bullets. He's lazy, has no ambition or passion in life and hates his job. His favorite pastime is to drink and pass out. When Sheppard visits him and says:"don't work too hard", he replies, "Don't worry it's against my religion".
The Stranger: The Dude, from Los Angeles. And even if he's a lazy man - and the Dude was most certainly that. Quite possibly the laziest in all of Los Angeles County, which would place him high in the runnin' for laziest worldwide.
Ryan Reynolds has done enough of a lite version of these guys that even when he landed a role as The Ace, the Hal Jordan from Green Lantern written for and played by Reynolds kind of turned into one.
Ron exhibits some of these traits in the Harry Potter series.
Victor Tugelbend from Moving Pictures aspires to being a student wizard forever. However, he keeps himself in good shape, because it's too much bother dragging all the excess fat around. And he has to study quite hard to ensure that during finals he comes just short of passing, but doesn't completely wash out of school. He doesn't see the irony in his situation.
The Slacker Handbook, a half-serious illustrated history/guide covering slacker fashion (comfort is key), assessing jobs for slack potential (able to turn up drunk and not get fired = win), perks (sleep, glorious sleep) and more.
Cameron, the main character of Going Bovine, is made of this trope, especially at the beginning of the novel.
A subversion in John Hemry's Paul Sinclair series beginning with A Just Determination: Commander Sykes, supply officer of the space cruiser Michaelson, is described as a slacker, even a "slacker god," because he's so laid-back, always hanging around the wardroom with a cup of coffee, never seen doing any work. The subversion is that he does do the work, and does it right, so quietly and efficiently that he has plenty of time to spend in the wardroom. This is pointed out by his immediate subordinate, who'd be in the best position to know if "Suppo" were pushing the work off on others. There's also an invocation of the Odd Couple effect, because the ship's XO seems like his polar opposite — except for the quiet efficiency they share.
Deckard in the Outlander Leander series. He's constantly being punished for slacking off, but punishments do nothing to motivate him.
Live Action TV
Most of the cast of That '70s Show. Especially Hyde, who is the smartest character on the show, but has no ambition or motivation to do anything but sit around in a basement.
Dave Lister in Red Dwarf, although later seasons do see him develop.
The Cat doesn't care about much other than eating and how good he looks early on. At one point, when told by the insubstantial Rimmer that Lister is in trouble, the Cat refuses to help until he finishes his meal (and he doesn't exactly speed up his eating either). Like Lister though, he too begins to contribute, though he is still remarkably narcissistic.
Tristan from All Creatures Great and Small doesn't take much of an interest in his studies despite being a perfectly good vet who probably could have qualified years ago if he'd applied himself.
Muriel from The Suite Life of Zack and Cody. She's close to retirement, but on several occasions she's neglected her duties. She once came into the Martins' suite and stayed there, eating all the food out of their refrigerator. She also walked in on a date between London and a boy, stayed there, and when London asked "Aren't you supposed to be working?" responded with "What's your point?"
A rare female example: Jaye Tyler in Wonderfalls. In one episode, she actually explains how she's created a "stress-free expectation-free zone" to live in. It is, however, shown in some episodes that part of her would like to accomplish something, she's just not sure what.
Like Jaye, George Lass of Dead Like Me (also created by Wonderfalls creator Bryan Fuller) is this at the beginning of the series. She puts it best when she says, "I excel at not giving a shit." She develops enough over the series to accept a promotion at her job and become a productive member of the team.
Mason also embodies this trope, preferring to steal from his reaps to get by, rather than holding down a job as the other reapers do (or are implied to have done).
Maynard G. Krebs, the beatnik sidekick in "The Many Loves of Dobie Gillis". As portrayed by a pre-Gilligan Bob Denver, Krebs would let out a panicked yelp of "Work!" at the mere mention of the word.
Grif from Red vs. Blue fits this pretty well. He snoozes through staff meetings and misses his duties to the point where Sarge stops assigning them to him because he knows they won't be done. Heck, the man himself admits he's lazy. At least one of the DVD profiles says that this is a plot on Grif's part to get himself discharged, but it wouldn't be a stretch to say he's normally like this.
Grif:I was born to take it easy.
Wally in Dilbert is based on someone Scott Adams worked with who, in order to take adavantage of incredibly generous severence pacakages, made a deliberately calculated effort to be in the bottom 10 percent of the company.
"La Nona" a (very, very) Dark Comedy by Roberto Cossa features Chicho, brother to the protagonist, who keeps claiming he is an "artist"... even though he never produces anything and lives by leeching off his relatives.
Rock from the Harvest Moon series. Fancies himself a ladies man and quite the catch, despite having no job, no desire to get one, and no obvious skills other than being pretty.
Karina of Rune Factory 3 is a female example, and one turned Up to Eleven. Most of her voiced dialogue has to do with her being lazy, her Artificial Atmospheric Actions have her falling asleep standing up, and she once tried to keep a diary, but her only entry was "Dear Diary, I decided it would be too much trouble to keep you, so I won't."
Dragon Quest VII has Hondara, The Hero's lazy Type-B uncle. He's a complete leech who constantly takes advantage of his brother/the hero's father's kindness, a hopeless lech, and a would-be Con Man. The hero's mother absolutely hates him and fears her son turning out the same way. The weird part? He manages to get his hands on several plot-important items. The Holy Water is real (and his neighbors are stunned to hear it), and the Hot Stone is a key item.
Gillian Clout from Atelier Annie, as well as the title character herself.
Neptune and Plutia in Hyperdimension Neptunia V are this seeing as they prefer to just slack off and sleep. The problem is that they're the CPU goddesses (equivalent to president) of Planeptune. Modern Gamindustri Vert is nearly as bad, as while she's motivated, it's entirely towards her MMO games and yaoi collection, and she uses such breathtaking Insane Troll Logic to justify her habits even Neptune thinks she's overdoing it.
Neptune's such a bad case that when she falls into an Alternate Dimension early on and wonders aloud where her alternate self is, Noire calmly posits that since this Neptune wasn't immortal, she probably died of starvation and self-neglect.
Darth Maul, of all people, in Ansem Retort. He literally passed up an opportunity to go to Hawaii because he'd rather stay home and crank call prostitutes. And he once called the producer of the show to get him to bring Maul the remote... which was four feet away from him.
David 'Walky' Walkerton of Dumbing of Age. He's admitted his slacking is partly motivated by simply not knowing what it is he wants to do.
Jenn from Sturgeon's Law works at the company only to fund her anime habit, and she doesn’t work very hard.
Mudd from The Book of Stories OCT. He has grown so laid-back and emotional, it affected his capacity to protect the Book of Stories, treating it with little care and then leaving his Twin alone to take care of the Book when he was confronted.
The title character of Daria and her friend Jane are the Brilliant, but Lazy versions. While studies come easy to Daria, and Jane is passionate about her art, they prefer to spend their afternoons watching Sick Sad World than achieve things that are expected of them. For Daria though, it's not so much that she's lazy, rather she simply doesn't care about a lot of things that most people do, and that there simply isn't much in Lawndale to challenge her in the areas she cares about.
Jane's brother Trent, however, is a more straight example of the trope. (He's very serious about his music though. Very.)
Daria was actually referred to as a straight-A student on an episode of Beavis And Butthead, an accomplishment rarely achieved by slackers. Although two of her classmates at Highland High School must have affected the grading curve substantially...
The Wombles, out of Britain, gives us Orinoco. While his Womble peers are hard at work clearing Wimbledon Common of humans' trash, he's usually looking for an out-of-the-way spot to catch another forty winks. Due to his love of sleep and Big Eater tendencies, he's also the fattest Womble (although he'd claim he's just "cuddly"). Elisabeth Beresford, the creator of the Wombles, reportedly based Orinoco on her then-teenage son.
Wade from Kick Buttowski. He's content with living at his stepmother's "basement" (a hole under her trailer), when he was promoted, he tried to be downsized back, and (when the "basement" was no longer a dwelling option) he once became spokesperson for a drink named "Slacker Z" in exchange for room at a businessman's tool shed.