I'd go with the Mad Max apocolypse. Basically the fall of government and devolution into tribal anarchy as countries fall into themselves vying for there own meager resources.
As the situation continues to spiral, larger cities become graveyards due to civil war, famine, fires and disease. Smaller cities become havens for whatever's left of government and corporations and those who can afford such protection. Townships, counties and towns with viable rural resources (ie mining, agriculture, fishing etc) will turn into villages either becoming feudal protectorates of the 'civilised' remnants or combining to form there own united comunities.
Amist the chaos of this dark age two different types of people will come to the for. Those that seek to destroy and those who seek to rebuild or preserve. The former will band together into decrepate bands hunting and preying on the weak or like the Lord Humongous will gather a hoarde and try to attack larger communities. The latter are like Papagalo and the Road Warrior one seeking to rebuild knowing that there is a better way of life. The other preserving the ideals of the past either as a vigilante (the road warrior) or as peoples gathering knowledge either to use to help or to catalogue and protect.
Well that's my kind of apocolypse anyway
im sure theres some hot alien girls who dont want our species to die out 
