I had an idea at the weekend for a game where mankind is under attack by machines and its greatest heroes and mythical beasts assemble to fight them off.
I'd make this as a computer roleplaying game, throwing together a raytracer I have with a pixel graphic single screen battle engine for the fights and have it run through a web browser. It would be an old school type game at heart, but instead of utilising the familiar classes or their variants (e.g. fighter, mage, cleric, thief) you'd recruit from heroes of legend and mythical beasts.
Of course, I'd probably need testers for it.
The idea of android villians being melted by dragon fire and turned into scrap is strangely appealing to me ;-)