Umm..Okay I dont know if this would fit in but I remember in a forum,for entertainment purpose, a game was created. I aint going into details just an idea of what it was.
The game was like a quiz, the admin/staff made a quiz in a poem like format and teams were made for members who wanted to participate.
There were separate threads for each team to discuss the quiz and all and only the members in that team could see the thread.
The hints for the quiz were posted around the forum and the members would search it and in the end the team would decide an answer and send it to the admin/staff.
There were like 3-4 quiz and the winner team was with the most correct answers and for a certain period the members of that team had a specific colour for their usernames like in SF admins have green and mods red.
So yah it kinda goes like this..