Both El Nino and La Nina at the same time. Due to the change to the Euro-dollar, a software glitch introduced by a Y2K date fix prevents a stock market meltdown. Investors would have been saved billions when what was just a 1-day panic was suddenly halted as the stock markets' computers crashed. However, a ruling by a Canadian judge forces the glitch to be removed since the comment describing the fix code was not written in both English and French. An exceedingly enormous comet is found to be heading to impact the earth within 6 months.
Aliens arrive to plunder the earth.
No, not illegal aliens. Aliens from UFOs. Since we're not going to be here to use it anyway, they just want to salvage as much of our resources as they can. In a final triumph of his newly found wealth, Bill buys up every computer running Linux and has them dropped one by one from the towers of the recently acquired World Trade Center. In the final minutes before the earth's obliteration, the gargantuan alien craft with much of the world's wealth departs for it's home galaxy.