The House/BSG crossovers. I consider them apocalyptical.
http://community.livejournal.com/parrotfic/10963.html
http://community.livejournal.com/parrotfic/9434.html
http://community.livejournal.com/parrotfic/9646.html
http://thedeadparrot.livejournal.com/353680.html
http://community.livejournal.com/parrotfic/11743.html

http://banishedfaith.livejournal.com/13414.html?view=69734

http://community.livejournal.com/house_wilson/945989.html#cutid1

http://community.livejournal.com/house_wilson/1266809.html?view=14655609

http://sexdrugsand.livejournal.com/4544.html?view=61120

http://timber-z.livejournal.com/11557.html

http://community.livejournal.com/house_wilson/878501.html#cutid1

I know there are tons more. If I come across any more, I'll post them here. Watch this thread.