They had a 'witchy' old lady next door that was constantly complaining
about everything and everyone in the neighborhood.  After one really good
round about kids and pets messing up her spotless front yard, my buddies
planned what turned out to be a better joke than they originally thought.
Juvenile as we all were, they planned to write some dirty words in her
meticulously-groomed front lawn with some kind of powder that would stand
out.  The only thing they could find was some Ortho Super-Gro Lawn Food
(white powdery stuff).  They wrote the message in the dead of night, and
next morning it was bold and white for the world to see.
The 'kicker' came after.  She came out, saw the graffiti, and immediately
grabbed a hose and WATERED IT OFF!

To this day, those sections of grass are just a little bit greener than
everything around them, and the words can STILL be read!



This reminds me of a story that a former roommate related to me.  In college
he and a group of friends got revenge on complete strangers.  ....Well, let
me set up the situation.

Y'know how sometimes you gotta park real far away from your destination
because certain types of people like to take up two parking spaces...?
Well, he and his friends got a little ticked about this, especially during
weekends at the school.  One day, they decided to get even with every
\verb+"#@@#\$#@$&&"+ that took up "their" space.  They turned the car sideways.
As he said, "He wanted that space so bad, now he can have it for a loooong
time!"