Our offices had the standard drop ceiling. I took a sausage balloon, filled it with hole punch confetti, blew it up and tied it off. Around the balloon I wrapped a very thing wire and then hooked it to some lamp cord which was run into the adjacent office. One side of a ceiling tile, over the victum's desk, was raised up and the balloon inserted to keep it propped up. When the victum came into his office and sat down at his desk a 12 volt battery was hooked to the lamp cord. The thin wire immediately got hot, popped the balloon (more like exploded), blew out the confetti on the person and desk. The balloon now collapsed allowed the ceiling tile to neatly fall back into place leaving the victum wondering what hit him.