Perhaps you recall the surprising lack of an apocalypse in May. While most media pundits simply claimed Harold Camping was wrong--we here at Illuminerdy look at the resulting non-apocalypse a little differently. Previously, we discussed the end of the world in the Mayan context. Indeed, across continents, cultures, and centuries, the end of the world has been anticipated many times, and with December 21, 2012 fast approaching, it is only fitting we discuss the gaming possibilities of the end times. Camping's revised estimate of October 21, 2011, also has passed sans-chaos. Normal folk may take this for granted, but you and I know better. Behold, I shew you a mystery (1Cor 15:51)
I have always been of the opinion that religious texts offer extraordinary ideas for games because they tend to be a collection of compelling stories. Shows like the movies Constantine, andEnd of Days, and the CW drama Supernatural reflect this idea quite well. Your games don't have to focus exclusively on Christianity, or even any real religion at all. Fantasy worlds are full of doom cults, soothsayers, and planet-destroying deities.
As a Gamemaster, you may be hesitant to implement this sort of idea into your games. This is understandable; should your players fail, the world you've worked hard to create for the players to mess around in will be over. That's the downside of the apocalypse. On the other hand, even should the heroes fail, the end times are ripe with adventure possibilities.
The Sky is Falling!
With so many doom predictions throughout the years, it certainly begs the question why the world has stuck around. In a game world, there are a multitude of possibilities for this, but the most exciting is that a group of earthly adventurers have always been around to step up and stave off the end times. Obviously, these holy warriors are sought out and tasked with stopping the apocalypse from happening. Perhaps an angel or even God himself requested these heroes (your players, reincarnated?) to once again save humanity from its destruction. It's tough to pass up on a quest from Heaven itself--the reward loot has to be pretty sweet, right?
While these ideas certainly lend themselves to a modern game of righteous PCs empowered by the Church to save humanity from darkness (obviously including an ass-kicking vicar, to take a page from Monsignor Martinez's Book), perhaps the strongest ideas come about when the PCs don't realize they are, in fact, causing the very tragedy they are trying to prevent.
Regardless, I would probably take the Terminator approach: you can't stop Judgment Day, you can only delay it. Indeed, within these story conceits is the the ultimate embodiment of the underlying concept in much of mythology and religion: the actions taken to avoid destiny often hasten its arrival.
End of the End Times?
Certainly an apocalyptic game is useful: it lays out a clear set of goals "you must find the six seals, the four horsemen, the twenty-four crowned elders, and Michael the Archangel's Sword." Furthermore, it should be pretty clear when your game is ended: the world should either be saved from destruction or it should be in shambles. Only Atlas has ever held such a burden.
The world (and your players) may laugh at people like Harold Camping and his goofy predictions, and may yet chortle at the impending Mayan doomsday. However, the safety of humanity in whatever world you choose is not guaranteed. It takes the actions and sacrifices of brave souls to stop the apocalypse. If that isn't a call to adventure, I don't know what is.