GOG.com (opens in new tab) are preparing for the coming apocalypse with their End of the World sale - a sort of everything must go event in which they expect everything to be gone.
Okay, so in reality it's just a particularly deal heavy, cataclysmic variant of the Christmas sale they launched last week. Highlights are too numerous to mention, but there are individual sales on The Witcher 2 (opens in new tab) and FTL (opens in new tab) , along with package deals on series like Might and Magic (opens in new tab) , Ultima (opens in new tab) and Telltale's adventure games (opens in new tab) .
There are also some themed bundles, best of which is probably the Cyberpunk and Steampunk (opens in new tab) , which will net you the first two Deus Ex's, all three Thief games and Anachronox. There's also some great indie stuff, like this selection (opens in new tab) of Introversion games that also comes with the brilliant SpaceChem.
The deal ends in around 22 hours, which is slightly before the civilisation turns off the lights. Although thinking about it, this probably isn't the best timing. If the world really does end on Friday, there's no way you're completing all of that.