One action per turn.
Unless you have a very good IC reason to be able to do this: 'Fred leaps into the air, turning somersaults to avoid the blast of the automatic weapon that had been shoved in his face. He lands with the grace of an Olympic gymnast, his hand moving swiftly to his side to withdraw his weapon from his holster as he swivels on his heel, turning to face his opponent. He aims his weapon at his opponent and fires a series of shots at him while his other hand wields the knife strapped onto his shin and throws it at the other guy next to him who begins to fire on him. He deftly dives out of the way of his blast as he throws the knife.' You can't.

Not only would it not be possible, but look at it. It is twinkie with a capital T. Use your best judgment as to your character's abilities and unless you are Quicksilver or someone with similar agility and accuracy, then do not do something like this. One action a turn will cut down on spam, confusion, twinkiness and time/later questions or arguments.