Sometimes we just can't resist giving a friend or relative a little fright. The classic way is to hide around a corner or just inside a doorway and when the target walks by, jump forward and say "Boo!" -- whether loudly or softly, either can work.
There are other ways to pull a scare prank. If you don't want to wait around, a well-placed rubber cockroach or spider will do the trick. If you don't have any fake bugs handy, you can simply point at someone's shoulder and yell, "Spider!" Television shows have staged far more elaborate pranks (for whatever reason, Japanese television sets the standard here). They've had giant boulders rolling down side streets, dinosaurs appearing in office hallways, and much more. Things like that are probably beyond your budget, but maybe a remote-controlled fish would be worth a try.
As you'll see in the video posted below, a remote-controlled clownfish (what else?) is put to good use. A woman is concentrating intently on something in the kitchen while the fish "swims" toward her, silent but deadly. She gets a good double-scare, first from the sudden poke to her back and then from seeing the unexpected visitor.
The fish is simply a helium-filled balloon made out of durable nylon with fins controlled by a remote control. It can ascend, descend, and turn left or right. This "Air Swimmer" is made by the William Mark Corporation, which has been in the flying toy business for over 25 years. If a clownfish isn't to your liking, they also offer flying bass and shark models.
