My Favourite is ''double, double toil and trouble; Fire burn and caldron bubble. Cool it with a baboon's blood, then the charm is firm and good'' and you guessed it is: MacBeth!! You?
What's this from? I confess that I haven't read them all. Of the ones I know, my vote goes to Macbeth. "Though Birnam Wood be come to Dunsinane, And thou opposed, being of no woman born, Yet I will try the last. Before my body I throw my warlike shield. Lay on, Macduff, And damned be him that first cries, 'Hold, enough!'"