I don't have a lot of experiences with one shots but I have read a few. One that comes to mind is "Emerald" by Hiroaki Samura. Known for his pornographic art and Blade of the Immortal.
As you can see below it's actually a story situated in America's Old West. Mainly about greed, land ownership, etc. The typical stuff really.
http://www.usaupload.net/d/3z4z8eqfd98