If you don't get caught - nothing. If you do get caught, you're looking at a mischief or vandalism charge, as I don't believe Washington is one of the states in which T.P.ing is considered legal.
You'd be a legend. Record it, upload to YouTube with fake info and fake email, from a Internet cafe so you can't get traced and you're set :)
You'd meet armed resistance and find yourself face-down - chances are Zero you'd succeed - they know if you penetrate the perimeter.