I plan on making Game Design my career, so I've thought up several dozen game ideas, most of which will probably never make it into existence. I'm not revealing them to the escapist forums though, not until i get them copyrighted XD
Ideas can't be copyrighted, only their execution (at least that's how it's SUPPOSED to work). Besides ideas are cheap it's all in the execution/details. Plus if you make something copyrightable then it's automatically copyrighted, you don't have to 'file' for copyright like a patent.
One of the ideas, that I'm definitely not planning on following through with, would be a Dwarf Fortress/Rogue-like game. The difference would be that you start out as an injured player of a race (elf, dwarf, human, etc.) deep down a cave.... alone... There would be no monsters, no intelligent npcs almost eerily nothing. The whole goal would be to survive get healthy, then try to find your way out. The gameplay would be centered around cultivating, herding docile animals, foraging for food, exploring without dieing, and crafting tools/items to help you out. The twister would be that you're not actually alone

. Explore far enough out or last long enough and you just might explore enough to actually encounter other creatures. There's no way I'd make the game as it'd take a serious investment on something that might not end up fun but if it worked out right I think it would be really cool to explore around trying to survive and finding interesting locales (ruins and the like that are abandoned) as you try to find your way out.