Whether it is plagues, giant asteroids, demons, alien weapons, nuclear war, or undead menace, the Apocalypse is never complete without its own special brand of horrible happenings. Over the years we have seen movies and books portray cataclysmic events in ever more interesting fashions, but still the method of our destruction remains pretty much confined to a few plausible choices.
10 - Alien Invasion - I think that most of us are picturing the incredibly ridiculous movie Independence Day on this one. It is not the only example of Aliens committing genocide and wiping out the human race, but it is one of the most prominent (and also the silliest in many respects). Say what you like, but this one is an all time favorite, and whether you are talking about The Arrival, Titan AE, or The Thing it all pretty much amounts to the end of the world if the aliens win. The problem is that no matter how advanced, smart, or powerful the aliens are, they will always be outwitted by the clever monkeys of Earth.
9 - Climate - OK, well, if you missed the movies The Core and The Day After Tomorrow, then you have yet to see the idea of ecological/climatological disasters at their finest. Though it is hard to convincingly see the idea of the planet itself as being the method of our destruction, many have posited this idea in fiction and in real life. Check out John Brunner's The Sheep Look Up for a good example in literature.
8 - Religion - Look out, here comes Jurgen Prochnow with the memos of the end times. Seriously, though, whether we are talking about Constantine, The Seventh Sign, or End of Days, the idea of biblical revelations has been a popular one in film and in print. Luckily for us, the gods have not yet decided to destroy the world, so Ragnarok is postponed for yet another day (sorry Thule Society).
7 - Outsiders and Beings of Madness - Call them what you like, but the Elder Gods scenario (much like the religious end of days scenario) has been one in many stories and films. From HP Lovecraft's work on the Cthulu mythos through movies like Hellboy, creatures from beyond the comprehension of many have always been a threat to the continued survival of mankind.
6 - Evolution - I am sure that the Neanderthals are laughing themselves silly over this one, but there have been a number of really great stories and TV shows about the evolution of humanity to its next step, and how that next step will eventually destroy modern man much as we destroyed the Neanderthals. My favorite example of this one is the TV show Prey which did not last anywhere near long enough to reach its cool prospective payout, but other good versions of this idea are things like X-Men, Firestarter, and Scanners (don't laugh).
5 - Frankenstein's Monsters - Man has a talent for inventing the method of his own destruction. Sometimes the destruction is more along the lines of a transhumanist concept, like the one in Netwon's Wake by Ken MacLeod, but more often it is something akin to the Terminator franchise. The issue here is, to quote from Jurrasic Park, "God creates dinosaurs, God kills dinosaurs, God creates man, man kills God, man creates dinosaurs..." "Dinosaurs eat man, woman inherits the Earth..." Killer robots, genetic experiments, and such will always be a staple of disaster stories.
4 - The Chain Reaction event - Much like the ecological and climatological stories, the Chain Reaction story relies on massive changes to the Earth usually brought about by things that are beyond our control. Unlike Climate-style disasters, Chain Reaction events are not the fault of humanity, but rather a more natural turn of events. Films of this type include such things as Sunlight, and similar themed movies and books.
3 - War - Although the Cold War is long over, the idea of war being the end of all life on Earth has still not disappeared from the collective unconscious. Although we are no longer balanced on the knife edge of mutually assured destruction, films like those in the Defcon series, as well as movies like The Day After, By Dawn's Early Light, and Failsafe still have a massive impact (just look at the TV series Jericho if you don't believe me).
2 - Meteors/Comets/Impact Events - These are always a lot of fun because in the long run there is really nothing we can do to stop a massive chunk of rock from hitting the Earth (assuming we even see it coming). Frankly my favorite of these films is Deep Impact which treats the subject seriously and works hard to make the story and the characters believable. Still, there is something to be said for the plethora of meteor disaster films.
1 - Plague - The Stand is but one of many stories that revolve around a world destroying plague. This idea has been around for a very long time, and will continue to have impact. Given disease scares like Avian Flu, Ebola, and others, the idea of the global pandemic is still topical and still really frightening. The long and the short of it is that this one is numero uno on the End of the World list because it will always be a potential problem, and is so common an occurance that it scares us all deeply.