If you want to freak someone out and test their ATC knowledge on VATSIM, request some obscure info via the Q-code, and issue a 'Pan' call. Then you'll see if they know their stuff.:rotfl:
http://www.qsl.net/sars/q-code.htm
http://en.wikipedia.org/wiki/Q_code
Yes, I know I am evil. Most of them will know QFE and QNH, but search the net for more, there are some really obscure Q Code calls.:rotfl:
On a more serious note, you can do ATC in FSX if you have the deluxe edition, which lets you operate the tower at an airfield. You can find a lot of people doing ATC on servers via FSX multiplayer. If you join one of these servers, I would recommend teaming up with another person who also has FSX and both flying in the same airliner, so that one of you can be P1 while the other works the radios. That's really quite good fun, and it is very stable too, which is one of the plus points for FSX.
Chock