hey, here's one of my favorite pranks to do, you have to choose the right victim though, they have to be kind of obedient and gullible. First fill a bowl with water, then stand on a chair and place the rim of the bowl directly on the ceiling. Next push the broom stick on the bottom of the bowl to keep it there. Then ask someone to "just do a quick favor and hold it there for a sec", then take the chair away and they are left there with no way out but to let the bowl of water fall on them. I'll try and find a video of someone doing it.
Here's one, its not too funny but you get the idea