The "finish the person above you's sentance" game
I dunno if this would work but here goes..
What I'm aiming for here is a never ending sentance where the person above you types something left open for someone else to finish.
(i.e. First person:The trees are green but the....
Second person: ...drink isn't very nice.)
You get the general idea, anyway I'll start...
"Alcoholic beverages....."