Paint a bar of soap completely with clear nail polish so it won't suds up.
Find a sleeping person, fill their hand with shaving cream and then tickle their nose.
Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.
I just recently discovered that there is a national holiday named after Atheism. April FOOLS day. Like this story in the name of Jesus.
Pull on a coworker is to press ctrl+print screen on their workstation, then paste it into Paint, save the pic, and set it as the desktop background. Move all of their icons to the trash. When they get back to their desk, clicking won't accomplish anything!
Hide an alarm clock in someone's bedroom and set it for 3:00 a.m.
April doesn't fool Chuck Norris, Chuck Norris fools April.
Change the coffee in the office coffee maker to decaf.
Put a "Please Use Other Door" sign on the entrance to your office building if it only has one entrance.
Install the Blue Screen of Death screen-saver on someone's computer.