I had a discussion with a fellow GM regarding the cold I caught and how the common cold is technically a plague due to it's qualities. This got us thinking about how bad it COULD get if the symptoms were worse, which became nightmare fuel for him.
For me, it's a brilliant idea for games, both campaigns and one-shots. The current one has the plague being a tool of an ancient civilization. It is a hive mind, acquiring memories and knowledge as it "infects" people. After a set period of time, the infection shifts and begins to transform people into members of that civilization (possession meets transformation), killing almost everyone else. The survivors are either immune (and fight back for the planet) or are only "resistant," still able to be infected and transformed at a moment's notice. Added bonus when you can't tell one from the other.
Now I think I have someone afraid of the common cold. . .
What other "nightmare fuel" discussions or events have you run into to inspire your games, or have even come up in a game you've played in? Have you had the chance to implement your ideas yet, or are they simply on the backburner waiting for a good game to drop them?