The rules are simple. You just have to insert something on the vending machine. Instead of inserting a normal coin, you can insert anything (just don't get overboard please :P) and the next person will tell the person who inserted something either the positive or the negative outcome.
Here's the example:
Insert an ordinary disc.
(positive) Comes out Hidamari Sketch DVD/BD.
(negative) Comes out Boku no Pico DVD/BD.
Insert a car.
(positive) Comes out Chevrolet Camaro
(negative) Comes out an old vintage car.
...and so on. Get it?
PS. Don't kill thread please. It'll spoil the fun. :(