Post your favorite pranks here...
i'll start with
1.
Take off the top lid of the victim's toilet. Look inside for the little rubber hose, the one that spits out water to fill up the tank. Now just take that sucker out of its holder. Put lid back on carefully so it just pinches the hose, which you have now aimed pointing out at the bowl. Since most people flush standing in front of the bowl they are gonna get soaked when (surprise, surprise) the water comes shooting out all over them.
2.
Simply visit any drive-thru of a fast food restaurant and attach a sign that says "Speaker is damaged, please speak loudly."
The next line of cars will think nothing of it and they will speak loudly into the microphone, while the order taker will be forced to hear people shout at them all day.
You may also want to sit inside and eat for awhile, since in most places you can hear the drive-thru orders from the dining area.
3.
1) Place an add on the net or in your local paper saying "Pass any drug test, any time, any where. $10.00. Guaranteed."
2) When the poor bastard sends you his money, you reply with a piece of paper stating these words "Don't do drugs."
I got these pranks here
http://gear.ign.com/articles/370/370036p1.html