The "anti-hero" comes to science fiction from a variety of sources, including noir and Westerns... but she also has her own uniquely science fictional avatars, that spring out of science fiction's tradition of skepticism and social criticism. The anti-hero is where science fiction's pulpy roots meet its most intellectual aspirations. Plus, he/she totally rocks on ice.

Noir:

My favorite noir hero is Dashiell Hammett's nameless Continental Op, who spends more time orchestrating convenient murders than he does investigating crimes. In the novel Red Harvest, the Op arrives in a town called Poisonville which is run by organized crime, and he systematically tricks the town's ruling gangsters into killing each other, first a few at a time and eventually in a full-on massacre. By the end, he's one of the few people left standing. In noir, nobody's morally pure.

The classic science fiction noir movie is Blade Runner, featuring Harrison Ford's hardboiled and conflicted cop, who's hunting the Replicants without being sure if he's doing the right thing. And of course Blade Runner is based on a Philip K. Dick's Do Androids Dream Of Electric Sheep?, and a lot of Dick's best work has a particularly noir flavor of pulpiness. Dick's protagonists are never sure if they're doing the right thing, and often are just out for themselves. That could be one reason why Dick is the author of choice for movie adaptations — his work is very close to a genre that movie people understand.

Another great science fiction noir author is Richard K. Morgan (no clue if the middle initial "K" is a requirement), whose first novel Altered Carbon is like a fusion of Chandler with Doctorow's Down And Out In The Magic Kingdom: hard-as-nails gumshoe Takeshi Lev Kovacs dies in a shootout, and then is restored from a backup and "resleeved" in a new body so he can investigate the murder of a rich guy (who's also been restored and "resleeved.") And then Kovacs promptly sleeps with the rich guy's wife.

And then of course, there's always Jim diGriz, hero of the Stainless Steel Rat novels, who starts out as an amoral trickster — before eventually devolving into a bit of a pussycat. And there's Gully Foyle, dubious hero of Alfred Bester's The Stars My Destination. (And Alfred Bester becomes the name of a morally gray psy-corps agent on Babylon 5, who becomes more of a sympathetic anti-hero in Gregory Keyes' novels.)

Westerns:

The archetypal Western anti-hero is out for himself, and only incidentally ends up helping others. Often, he (and it's usually a "he," except for Sharon Stone in Sam Raimi's underrated The Quick And The Dead) is only a "good guy" in comparison to the really really shitty bad guys. Think Clint Eastwood's Man With No Name from the spaghetti westerns. Cowboy-influenced anti-heroes in science fiction are usually pretty easy to spot: Han Solo in Star Wars and Mal in Firefly have everything except the Ennio Morricone whistle/trumpet score playing in the background.

I'm also going to peg Vin Diesel's Riddick from Pitch Black as a Western-style anti-hero — he's basically a convicted murderer being transported across the prairie in a wagon train, and then the wagons break down. Will he help save his captors, or let the elements and the hostile natives take care of them?

The Mad Scientist:

Unlike the noir and Western anti-heroes, the mad scientist has always belonged to science fiction, as far back as Frankenstein and Dr. Jekyll And Mr. Hyde. As the name implies, the mad scientist doesn't always have the greatest grip on reality, unleashing forces he cannot blah blah blah. The mad scientist is often just a foil for the hero in space opera and action-adventure stories — but he's also a protagonist a surprising amount of the time.

On TV, Doctor Who features a mad-scientist archetype as the hero, and the early episodes of the series in the 1960s made a conscious effort to portray the Doctor as an anti-hero rather than a more uncomplicated good guy. Over time, the Doctor became purer and more motivated by compassion for other sentients, but he still gravitates back to the anti-hero side of the fence occasionally, most notably in the late 1980s.

Cyberpunk:

Cyberpunk obviously borrowed a lot of themes and styles from noir, but also brought in its own flavor of anti-authoritarianism. The e-zine Computer Underground Digest debated, in 1991, just how anti-heroic the cyberpunk hero actually is. Brad Hicks wrote:

A cyberpunk is to hackers/phreaks/crackers/crashers what a terrorist is to a serial killer; someone who insists that their crimes are in the public interest and for the common good, a computerized "freedom fighter" if you will.

In the works of Bruce Sterling, William Gibson, and others, cyberpunks are not terrorists in the conventional sense of the term, and the analogy to serial killers strikes me as a bit extreme. Cyberpunks are characterized by their resistance to oppressive authority (which makes them a form of freedom fighter), but the resistance tends to be highly individualistic. I wonder if cyberpunks might be based on the anti-hero model of westerns (Shane) or earlier science fiction in which the marginal but basically decent outsider steps in to use marginal skills to save the town, country, or civilization?

The rationalist skeptic, who critiques everyone else's ideals and delusions, is an outgrowth of the mad scientist, and usually has some scientific knowledge. But he's also a nihilistic superhero, who questions human-made belief structures. Avon from Blake's 7 is a bit of a mad scientist and a noir gun for hire, but he's also something else — a foil for rebel leader Blake's idealism who grows into a self-hating amoral hero in his own right. Avon serves as a role model for Horza, the bitter mercenary in Iain M. Banks' Consider Phlebas, the first Culture novel. The shape-shifting Horza tricks a shipfull of pirates into helping him track down a lost Culture Mind in the middle of a warzone. He's willing to make deals with his worst enemies and double-cross his friends, if the job requires it.

The Vulture, from Salvage 1. Andy Griffith is "a junkman with a dream," in this ABC TV movie that became a series. He decides to build a spaceship from junk and fly it to the moon, so he can reposess all the crap that NASA left up there and sell it back to NASA (or someone else) for a profit. He enlists the aid of a retired astronaut and an "explosive" fuel expert, and together they pull off the impossible. Is it legal, someone asks him. "I don't know!" he replies cheerfully. Here's another clip:

The Yamato, from Starblazers. The Earth is being devastated by radiation bombs from the evil Gamilons (or Gamilas in Japanese). The Earth's space fleet is ruined and outclassed. There's only one hope left: travel to Iscandar and get a miracle cure from a glowy princess. But there's no spaceship to make the journey. So the surviving humans find the ruined World War II Japanese battleship Yamato, and retrofit her into a spaceship. For years, I wondered why the Yamato looks so boat-like. Then I re-watched some of the DVDs and found out why.

The Thunder Road, from Explorers. Ethan Hawke, River Phoenix and some other guy learn how to build a device that creates a space-worthy bubble, from their dreams. Using this for protection, they build a spaceship out of an old Tilt-A-Whirl amusement-ride seat, washing machine windows, a spare tire, old TV sets, and a "proceed with caution" sign. Then they actually fly their home-made contraption up into space and meet up with aliens, led by Robert Picardo, the holographic doctor from Star Trek: Voyager. (Thanks to Sherilyn for the tip!)

The 747, from Star Smashers of the Galaxy Rangers by Harry Harrison. Possibly the silliest book by Harrison, who also wrote the Stainless Steel Rat and Bill The Galactic Hero books. In this parody of golden age science fiction, three guys and a girl are playing around with a home-made particle accelerator. They put some cheese in the accelerator's target area and create a new element, cheddite. It has the ability to move people immense distances across space, so Chuck, Jerry, Sally and John turn an old 747 jet into a spaceship and fly across the galaxy. They find themselves having to save the galaxy from an evil race known as the Loathesome Lortonoi. (Thanks to Alan for the suggestion.)

The Barnyard ship, from The Astronaut Farmer. Billy Bob Thornton gave up on being an astronaut to go home to his farm, so he decides to build his own rocket in a barn and fly it into space. He doesn't really build it out of junk, however, so I'm not sure if it belongs in this listing.

The Madball ship, from Madballs. This is a cartoon tying in with a gross-out candy from the 1980s. On a planet where everybody is a ball with arms and legs, the evil Badballs want to ban rock'n'roll. The bastards. So the Madballs build their own spaceship out of parts they find by dumpster-diving (they literally find the final crucial piece in a trash can.) And then they fly to Earth, where they can have all the rock'n'roll adventures they want, and never be heard from again.

Rickety Rocket. A group of stereotyped black teenagers create their own spaceship out of garbage they find, and they use it to solve mysteries. It looks just like Speed Buggy and has a similar origin. The cartoon aired as part of the Plastic Man Comedy-Adventure Show. Typical storyline: A robot art critic in a top hat (classy!) is stealing priceless objects and shrinking them using a matter transformer. But he turns out not to be a robot after all (boring!).