I got pranked this weekend and the boys thought it was the best thing ever. It's an easy one too - perfect for April Fool's Day.
You just need a water bottle and a pin. Fill the bottle pretty full with water. Over the sink poke holes all around the center of the bottle.
Wait until the water stops dripping, very gently wipe off and place on the counter somewhere you know it will get seen and picked up.
When someone finally picks it up (I did in frustration of the boys leaving things out everywhere)...
Yep, you get sprayed. It was pretty funny. This works best with the thinner plastic water bottles. Have fun!
(Obviously young kids should be supervised when using needles)