Rather a lot, actually, but mostly, 'A plague on both your houses for they have made worms' meat of me.'

It is Mercutio who says "a plague on both your houses!" after he gets stabbed by Tybalt

A plague on both your houses!

Mercutio is the character who yells the quote 'A plague on both your houses!' in the Shakespeare play, Romeo and Juliet.

The character who yells "A plague o' both your houses!" is Mercutio in William Shakespeare's play "Romeo and Juliet." He says this line after being fatally wounded in a fight between the Capulets and Montagues.