Out of all of the Avengers, Who Would Win in the Ultimate Battle?

Out of Iron Man, Hulk, Captain America, Thor, Hawkeye, and Black Widow, who would prevail?

Source: http://forums.ufc.production.sparkart.net/showthread.php?t=117682&goto=newpost

Ian Freeman Don Frye Tony Fryklund Kazuyuki Fujita Masakatsu Funaki