These are some really old ones, but depending on your school you can play around with them…:
1)hiding a tape recorder in the ceiling with a tape of someone banging and saying help me, let me out of here
2)hanging ice cubes from the ceiling in the hallway (just make sure not in an area where pple will slip, and clean up afterwards!)
3)change the names on the attendance sheet to some other more interesting ones… (just don’t write a name that will embarass you!)
more to follow…