One idea that constantly occurs to me, after I've got past the world building of most of my novel plans and the like, is the idea of having a main character who is not the character through which we view the story. I don't just mean by having the story in third person omniscient either, I mean by having the standard third person view but multiple POV characters who all interact with the character about whom the story and plot is.
Put another way, it would be like reading Bernard Cornwell's Sharpe books but from the points of view of Harris, Harper, Wellington etc rather than centring on Sharpe himself. So you'd have the story of Sharpe's Rifles told by various members of his regiment, with Sharpe appearing at various points, then a gap until he appears to rescue Harper and the rest from the ambush and so on and so forth. It would be very difficult to write but it would be really interesting. Mainly to see if I could actually create that many realistic characters who would be 'real' enough to follow. Each one would have their vignette and, slowly, it would become apparent that the plot was following someone else, someone who featured in all of the other stories.
I'd have to actually write it, though, and the lack of posting here would seem to suggest that this would be difficult. However, the point of this blog is to spur my typing and I seem to get a groove on every year. When it happens this year I just have a place to put it all.