I came across an interesting bug the other day, mxmlc started complaining loudly about a newly created string definition. My first instinct when I get weird compiler errors like this is to simply comment out the line and make sure the compiler error wasn’t created because of a dangling bracket. To my horror the newly converted comment was creating a compiler error!
To cut a long story short, if you copy text out of a textField inside the Flash CS5 IDE (Mac) and paste it into Flash Builder, you will copy out the trailing null character! What is even more fun, is that it is invisible in Flash Builder, the only way you can tell it is there is because navigating across it will swallow one key press. Luckily Vim shows the null character as an obvious ^@ character.
Finding a way to prank someone with this knowledge is an exercise I will leave to you, but I have a few ideas myself. 