Warning: Playing practical jokes with Dynamics GP can get you fired. I’m not responsible if that happens. None of these practical jokes can actually harm a Dynamics GP system UNLESS someone screws things up trying to troubleshoot what’s going on. Use any of these practical jokes at your own risk.
For companies not using Account Security, a simple prank is to turn it on using Setup > Company > Company and checking the Account Security box. For all users but ‘sa’ the chart of accounts will seem to disappear. Hilarity, and possible violence, will ensue. Unchecking the box makes the chart visible again.