From the Wikipedia page on Space Exposure:
The key concerns for a human without protective clothing beyond Earth’s atmosphere are the following, listed roughly in the descending order of mortal significance: ebullism, hypoxia, hypocapnia, decompression sickness, extreme temperature variations and cellular mutation and destruction from high energy photons and (sub-atomic) particles.
From In Science Fiction:
Spacing is a staple of science fiction,[13] where it usually occurs as a method of execution (or other sort of killing) by vacuum exposure in space - usually accomplished by ejecting the subject through the airlock of a spacecraft or space station without a space suit. The primary cause of death would be asphyxia. Many films show people exposed to vacuum in unrealistic ways.
* <PERSON> of the Aliens series is a particularly adept spacer, having defeated xenomorph adversaries with at least 3 different forms of spacing. Two of the methods involved fully jettisoning the creature into space, with the third having it slowly (and quite graphically) pushed out through a small hole in the hull.
* Movies such as Outland and Moonraker show people exploding in a vacuum.
* 2001: A Space Odyssey, A Trip to the Moon, From the Earth to the Moon, and several episodes of Doctor Who show people surviving a vacuum with no suit on.
* Battlestar Galactica and the film Sunshine, show some people suffering after a short exposure, and others dying plus freezing from longer exposure.
* In one episode of Farscape, <PERSON> leaps through space from one ship to another without a suit. His exposure only lasts several seconds and he survives without any permanent damage, but is shown to be in considerable pain afterwards.
* In Total Recall, the character of <PERSON> can survive near-vacuum conditions just by holding his breath.
* Several recent films, such as Mission to Mars, show people freezing instantly in a vacuum.
* In the episode Tangent, on the TV show Stargate SG1, characters are perfectly fine even after being exposed to space for about five seconds.
* "Spacing" is a common topic in Babylon 5, used as a joke and referenced as a punishment for Mutiny and Treason (the only law left in earth that still permits execution). 947
In the season 2 episode And Now For a Word Dr. <PERSON> describes an experience of witnessing someone die as a result of exposure to space.
* Event Horizon shows it in a very graphic example.
* In The Hitchhiker's Guide to the Galaxy, <PERSON> and <PERSON>, after being found trespassing on a <PERSON> spacecraft, are sentenced by <PERSON> to die in the vacuum of space (after <PERSON> and <PERSON> heard a bit of <PERSON> poetry first). Within 30 seconds of ejection (and at an improbability ratio of 2 to the power of 276,709 to one), they were rescued by the Improbability Drive ship Heart of Gold.
* In Wait It Out, a short story by <PERSON>, two astronauts are stranded on Pluto, but don't die: in those temperatures their brains becomes superconductors.[14]
* In <PERSON> Honorverse, slave traders who haul their "cargo" into space to get rid of evidence are tried as mass murderers and sentenced to death by spacing.
* In the movie Titan A.E., <PERSON> and <PERSON> escape from a small space vehicle by exhaling, holding their breath, smashing out the already cracking front windshield, and floating into space just in time to be picked up by the spaceship Valkyrie. They both pass out in the landing bay.
* In the video game Star Wars: The Force Unleashed, <PERSON> apprentice is thrown out of a window aboard <PERSON>'s Super Star Destroyer, and is exposed to vacuum for an undetermined period of time (measuring at least several minutes). He is retrieved by a recovery drone, and appears completely healthy six months later (however, the physics of space in Star Wars has never been explained, with questions originating from trivial matters such as the fact that fire-explosions can occur in space as well as noises being heard, though the latter is common to many sci-fi movies).
* In the video game Mass Effect 2, Commander <PERSON> is thrown from the Normandy after it is attacked by a Collector Ship with a punctured suit. <PERSON> is recovered by Cerberus and is brought back to life.
* In the episode Ariel, of the Firefly television series, <PERSON> is threatened with spacing as a punishment for selling out two fugitives who were part of the crew. 569