I've made some progress scripting a comic whose concept has been bouncing around in my head for years now. It's been coming along nicely.
Initial set up is for a hitman (or hitwoman, in this case) to basically decide she wants out after running into a hit (performed by someone else, of course) so perfect there's no longer any reason for her to pursue the fine art of murder. The plot goes a little further than that before it flattens out into broad sketches, but what explication I have so far mostly covers that bare premise.
Just to give you an idea of how long this has been rolling through my mind, this sketch is from 2002 at the latest.