Some time ago I read here one post about the voice mail. I'd like to add my ideas to such tricks.

In fact there are plenty of different jokes, which you can record for the voice mail. And I usually do it to have fun, as it's very interesting to see how people react.

My friends, for example, like to leave the following messages:
"Hi, it's me- voice mail. My boss is out for God's sake! Now we can have a free talk!
Or.. if you don't know what to tell me, let's keep silence together!"

And this one is great, I think:
Imitating the cheerful DJ voice you say "And here it is the listener, who is lucky to call us first! Please, be attentive, after the special signal he will sing a song for us to win the prize! Are you ready? Go!"
Usually there is a long silence, or the person quickly hangs up the receiver. But there are cases when the person really starts singing!

I believe that the voice mail is still the best way to laugh at people!
May be you know some more