To me, there is a difference between an army and a project. An army is usually designed for gaming, but there is often a fluff component. A project is usually fluff based, and isnt always designed to be an army, but can and often is used as one. By this logic, roughly half of my armies are projects.
Projects can be anything, from a single squad that you decide to give a unique paint job and history, up to attempting a full battle company or even a Chapter, for the truely insane.
My current project (the Crusade) is one of the more insane ones Ive heard of, but not one of the most insane that Ive had. Once upon a time, I was planning on making a 2000 point army for each of the Traitor Legions. Ive still got some of the Iron Warriors, Night Lords, and Word Bearers sitting around, but most of the work ended up going into my Black Legion, sitting somewhere around 5k points these days. I was also looking at doing the same with the First Founding.
So, once again, Im looking at my Crusade, still sitting on my shelf (I think this is a record for how long an army has remained set up there), and trying to tell myself that I need to finish this before I start another project, though the idea of adding at least a single squad from each of the First Founding is getting better and better. Really, all Id need is Blood Angels, Space Wolves, Iron Hands, White Scars, and Raven Guard... The other four already have at least a single tactical squad.
So, anyways, what I was trying to get at is what are some of the projects you have done, seen, or heard of? Ever have the great idea for one, but never got around to it?