So here is my one million idea:Chesscoin!
Two coupled coins: Whie and Bllack (WCS and BCS)
One the main webpage there is a game between two very good chess AI. And dependent on which team (black or white) has more points the difficulty and block reward is changing.
The AI make one turn in a day. After the game is over: Diff and reward resets and new games starts.
That will be pretty interesting, since you dont know if losing team with low diff will suddenly win:)
Very interesting concept. Maybe not for an altcoin by itself, but would certainly serve as a proof-of-concept app for something like BitShares or Ethereum.