LoL Character Creator
For me personally just a dream of the perfect MOBA, but in LoL possibly a fun game mode with a chance to evolve into something more serious in the long run? Create your own champions based on the database of existing champions. Freely mix and match model, abilities and passives yourself, from any number of existing champions. It could be a creative contestant to URF that replaces sheer randomness with thought and creativity. It worked for City of Heroes, it might work for LoL and if nothing else, I am sure it would at least be as fun as URF.
I mean, seriously, who wouldn't want to see an Ahrision?