Me and my band teacher did this one, and it's actually pretty damn good.
I used to play some clarinet back in like 7th grade I think it was, so I always sat right up at the front of the band in front of the band teacher. Anyways, he comes in on April Fool's day, and starts giving his usually spiel about what we'll be playing that day. At some point, I made some stupid comment, that most of the band couldn't even hear, and he gets SUPER mad at me. He would get mad fairly often, so it wasn't totally unbelievable, but he was way more mad than we had ever seen him before. He starts yelling at me, and I talk back to him a bit, at which point he yanks the clarinet that I'm holding out of my hands in anger. Now in our band room, there was this door out to the fire escape about 30 feet away from where the conductor's stand was. During the spring/summer, our director would always keep it partially open to let in the warm air. So he takes the clarinet that he just grabbed from me, and chucks it across the room, right at the fire-escape door. The clarinet hits the door, and shatters into about five different pieces, most of which fly out onto the fire escape. The class literally went silent, they were in such shock.
The clarinet that he threw was in reality an old broken one that he had given me before class, with the two of us planning the whole thing out. That said, I didn't actually realize that he intended to throw the instrument all the way across the room, so my reaction to that was quite genuine. It was a good time.
