What's your favorite Noob (FNG for the military types) trick or prank to play?

Ours was have the new guy go over to personnel and tell them he needed a unit ID card made up. He had to submit the request in writing to the head of the Admin unit. The form he had to request was called the "IDentification form 10 Type"

Seeing the face of the FNG requesting an "ID10T" form was priceless!