Last year, I GM'd a seven week RP here about the explosion of a massive nuclear reactor plant that was the essential end of the world. People were trapped inside the largest city in the world, with no way to escape, and would die when the bomb exploded in seven days. I had to be kind of strict on the timing though, so things didn't turn out quite right until the end
It had some of the most brilliant storylines, characters, and themes of any RP I've been a part of... at least until the last week, when it really really slowed down. But all of it was great. Everything was possible in the world of lawlessness, or rather, nothing was possible. Unceasing Crime, complete moral fallout in the perceived absence of God, those who still believed in God, those searching for a God... and a man dressed as Santa Claus giving bomb filled teddy bears to little children. It was a practice in Absurdity with alot of amateurish philosophical themes, but it was a lot of fun.
The problem was that I had major plans for my psychotic killer's character (And his illegitimate mute daughter) to develop... and there wasn't enough time to close it all up. It was fitting though. Everyone died suddenly in vain, and it was over. The end.
Nobody reads old RPs like I do, but here's the link anyways:
http://www.christiananime.net/showthread.php?t=53503