This (http://www.alphaboard.com/) would be a interesting trick to play on someone. Just replace their keyboard with this. You could always rearrange the keys to appear as a normal keyboard and watch what happens when they try to use it.

http://www.alphaboard.com/images/keys3.jpg

if on the off chance I decided I want to screw with my typing speed, I'd go with a Dvorak keyboard.... not that thing