Best Way to Ruin Someone's Day

Is there someone that you really hate, or a friend who you want to mess with? Well here is a simple but horrible way to do just that. It works as a direct attack or a booby trap, the booby trap is much more devastating. This is short and cheap and simple. I know it is easy but figure why not mention it. No pics because it's simple.

If you've every played with party poppers, you know how much fun they can be, but have you every dissected one? Inside is a small pull firework. When you pull the string, it ignites and the pressure blows of the cap and send confetti out. But you can replace the confetti.

Glitter is good, makes people look stupid.
Flour is more noticeable.
Itching powder is great.
The best and most painful is capsaicin powder. You can make it from ground peppers or buy it. Although you need to hit them in the face. WARNING, this is very painful and can lead to assault charges and injury.