I have some highly placed sources that tell me this WILL happen within the next 5.5 years...
First the Chicoms and N. Koreans will launch simultaneous attacks against Taiwan and S. Korea, respectively. US will respond in force to protect their allies in this region, with the aid of the Russians who finally get to settle their differences with the Chinese over Marxist doctrine.
Taking advantage of the chaos, all hell will break loose in the Middle East with old enemies (i.e. Everyone vs. Israel) coming to life. Israel will call upon their long time protectorate, the US to assist, further stretching the resources of the US Military.
The Mexicans and Canadians, sensing a rift in the balance of power, will execute a joint invasion of the US, citing "years of oppression" in their declaration of war.
The United Nations will land troops on US soil, in order to "maintain peace" in the region, while secretly using the US invasion as an excuse to begin it's disarmament of US civilians.
Israel, in a last ditch effort to save themselves, will launch and all-out nuclear assault on it's enemies, reducing the region to a glowing nuclear playground. India and Pakistan, jealous of Israel's display, will nuke the crap out of eachother.
That's the fan, now here's the shit.
Muslim fundamentalists, angry with the decimation of their beautiful deserts, will launch a full scale bio-chemical assault on the US, using terrorist cells well established in the major metropolitan areas of the country.
The bio-toxins will have an unexpected reaction with the radioactive cloud now covering the earth. The resulting virus will have no apparent effect on the living, but will cause the dead to rise from their resting places.
The dead are hungry and pissed off, because, well, they have been dead!
So what one weapon do you arm yourself with???
I will be armed with an M4 with beta C-mags equipped with a KAC RAS. On the bottom rail of the RAS will be a M203. On the right and left side of the RAS I want a Rem Masterkey 870 magnum for each. I will rig up a trigger mechanism that will simultaneously fire the M4, the M203 and the two 870s. I also need a visible and IR laser, because I heard the dead don't like lasers in their eyes. Oh and a PVS-14 and tac lights, 'cause Zombies like to fight at night.