Kinds of papers

I've seen some recent writings about how theory papers come to be, and it got me thinking a bit about how experimental condensed matter papers come about, at least in my experience. Papers, or more accurately, scientific research projects and their results, seem to fall into three rough groupings for me:

• The Specific Question. There's some particular piece of physics in an established area that isn't well understood, and after reading the literature and thinking hard, you've come up with an approach for getting the answer. Alternately, you may think that previous approaches that others have tried are inadequate, or are chasing the wrong idea. Either way, you've got a very specific physics goal in mind, a well-defined (in advance) set of experiments that will elucidate the situation, and a plan in place for the data analysis and how different types of data will allow you to distinguish between alternative physics explanations.
• The New Capability. You've got an idea about a new experimental capability or technique, and you're out to develop and test this. If successful, you'll have a new tool in your kit for doing physics that you (and ideally everyone else) has never had before. While you can do cool science at this stage (and often you need to, if you want to publish in a good journal), pulling off this kind of project really sets the stage for a whole line of work along the lines of The Specific Question - applying your new skill to answer a variety of physics questions. The ideal examples of this would be the development of the scanning tunneling microscope or the atomic force microscope.
• The (Well-Motivated) Surprise. You're trying to do either The Specific Question or The New Capability, and then all of the sudden you see something very intriguing, and that leads to a beautiful (to you, at least, and ideally to everyone else) piece of physics. This is the one that can get people hooked on doing research: you can know something about the universe that no one else knows. Luck naturally can play a role here, but "well-motivated" means that you make your own luck to some degree: you're much more likely to get this kind of surprise if you're looking at a system that is known to be physically interesting or rich, and/or using a new technique or tool.

Hopefully sometime in the future I'll give an anecdote or two about these. In the mean time, does anyone have suggestions on other categories that I've missed?