I had an idea a while ago that I thought was pretty strange and fun.
You play as a hero who is aware of the fact that he's in a really REALLY badly designed game.
Like, he knows that the enemies are rigged so you can't beat them. And he knows that all the health upgrades and secret cool weapons are out of reach in stupid places.
And little things that you're supposed to be able to do, you can't, because of bugs in the level, or scripting or whatever.
(You know the way Daffy Duck complains to the artist who's drawing him? Yeah. That sorta vibe!)
So what can this hero do in an unbeatable land that was designed to frustrate and kill him? He cheats.
The goal of the game would be to find glitches and cheats in the game -- stuff that would be impossible to do in the real world -- but totally plausible in a game world. You guide the hero around finding ways to "glitch" your way past problems and cheat death.
It's so much fun to hack games and do the things you're not supposed to do. Why can't that be the whole goal of a game?