On The Last forum i did this on we got 2 pages of posts, lets beat that record!
The first person says a wish.
The second person says "Wish granted, but..." then he has to avoid the wish.
For example:
First poster: I wish I was a millionaire.
Second Poster: Wish granted, but I stole all your money.
I wish that I could get covered in pixie dust and then be able to fly!
Third poster: Wish granted, but I stole all your pixie dust.
I wish that I had a life time supply of beer
etc. so I'll go first
I Wish for a Sports car