Recolored to colorize black & white photos with relatively little effort (or selectively remove color from a color photo.) Get it while it's still freeware!
It's really useful already, but for certain situations, it would be really handy to use a customized coloring method. For instance, I've found that in several situations you might want to automatically vary the color according to the brightness of each pixel. This would be useful, for example, when coloring a tree with dark leaves against a bright sky background, when coloring certain breeds of cats, or when coloring a chain-link fence in front any colored surface. In these cases multiple colors are mixed very closely, and manual coloration is very tedius.
There are other tweaks to the algorithm that would be useful also; for example, coloration based on texture, or varying the color saturation according to brightness. A quick preview or quick color test feature would be extremely handy.
Which brings me to my talking point... if only the program were open-source, one could make the changes one wants all by oneself. One could also take the very cool coloring algorithm and insert it in other programs such as Photoshop, Paint.NET or The Gimp. Now, the wonderful world I've described before in which almost everything is open source won't become reality any time soon, but here's an idea for getting specific programs to go open source.
There is a website somewhere where people can make proposals with a monetary requirement (such as "release Recolored under the GNU GPL for $20,000") and other people can pledge money to it. But, er, I lost the address of the web site. Anyway, I wonder how many products could be coerced into freeness in this manner. If it's practical, maybe we could make a movement out of it. The movement's job would be to negotiate prices and terms with software vendors, and then to create awareness and convince people to make pledges.
Mind you, it would probably work only with a whole ton of pledges, so we'd have to rely on non-geek support. It would also require that many people who would otherwise just buy a licence be convinced to make a pledge instead (or in addition)--a tough sell, for the most part, I think.
There are other problems. Merely open-sourcing a program doesn't yield the desired features, of course. And the code quality of a closed-source app is inestimable. Are there a good set of code comments? Function- and class-level docs? It the code structured like a house drawn by Dr. Suess? There are a lot of open-source programs that don't get touched due to such issues.
In summary: this idea might suck. Still, there are probably situations where this could work.