Niche
Programming almost has no limits to the type of software that can be created. Don't we program to make things easier? So think of all the things that annoy you when making a game, and think of a program that will solve it.
Audio
So, for the most part, there are bunches of software dedicated to complex graphics manipulation, but not as much attention is dedicated to audio. The most useful audio software I have used was Reason 4.0 because of this:
Sound manipulation at it's greatest. You can surely use this software to create your own sounds. We have efficient ways of describing shapes, but how do we describe sounds? We have primitive shapes that can be sculpted into any shape imaginable, but are there primitive sounds we can sculpt into the sound of a human laughing? So of course, I have downloaded plenty of text to speech software, and my favorite one right now is the "Speak it" app for the ipad.
DIY Development
Making games is too specialized. I don't think it should be so specialized, because there are plenty of people who can create amazing things, so long as the tools they use are straightforward and easy to grasp. A game engine that makes games amazingly easy, just like Google Sketchup makes modeling easy. Or just like 3-sweep makes modeling much easier. The reason I am learning programming is to perhaps be able to make my idea of the perfect game engine (high hopes). What about a software that makes making software easier? I really loved that 3DFA software. It stopped development suddenly. This way people can make their own custom software without having to hire developers (I am sure some would not like this idea though.)
Think outside the box
So, Marvelous Designer was long overdue. I tried to find alternative software, and found a free one that was good enough, but VF Pro just fell of the map. Fashion has been around so long, so such a software taking advantage of 3D modeling was just a "duh" to me. I can think of other areas where 3D would serve very well. Google sketchup already has the Engineering industry on lock, or should I say "Trimble Sketchup."
I don't want to turn this into a diary though. haha. But there are so many areas to be explored, so I don't really see a limit on what can be made.