Game Mode Idea: Permanent Paranoia
I wonder what it would be like to play a Summoner's Rift game with a permanent Paranoia-like darkness in which you only see what is around your champion. You have no idea where your team mates and enemies are.
And all wards are permanent (but can still be destroyed when seen). So many new possibilities arise from this!
I think this would be a great Halloween idea. It could also be a vs. Bots only mode with random spectral or ghost-like champions popping out of brush (similar to Garen in the Doom Bot mode); they could use one ability on you, chase you for a few seconds, stand there and laugh, or just run off in a random direction and disappear.