Heres another really fun forum game that I remember seeing in other places:
The person above you makes a wish, the next poster grants that wish, but with a really sinister or unpleasant twist, like a genie.
For example:
Poster 1: "I wish I was warmer"
Poster 2: "Granted. You are now stuck inside a furnace. Enjoy burning to death"
or on a slightly less grotesque note:
Poster 1: "I wish I had a bigger bedroom"
Poster 2: "Granted. Youve been shrunk to the size of a mouse. Enjoy the extra space"
And once youve corrupted the wish of the person above, you make a wish for the person below you to corrupt, and so on.
ahem
I wish I was at Disneyland.