You might be interested in the Opps Daily [1] newsletter. Every day is someone describing a software product they would pay money for.<p>[1] <a href="http://www.oppsdaily.com/" rel="nofollow">http://www.oppsdaily.com/</a>
These types of questions always gives you horrible answers.<p>Go to a forum, or StackOverFlow, and see what people want that you could make a tool out of.
A machine with can print legit money in any currency I want. I would definitely pay for that.<p>On a more serious note, I have a few workflow problems which will definitely make me shell out few bucks if there is a polished product.<p>In fact, i have more than a few. I'll give you one example. There should be a really nice cross-platform diff viewer for people who use git from the command line. My reasoning for that is that i like using the command line for git because it is way faster than GUI, but i always end up using the terminal for viewing diffs and stashes.
42.<p>On a more serious note; just in case.<p>- A tool that combines logic of my source control (commit history), static code analysis, and my ticketing system to produce a risk matrix for my code components so I can better estimate how risky a feature or bug fix is to implement. I.e. Many commits in a short amount of time, with multiple issues reported in that code area and bad static analysis results probably means I need to rewrite that part entirely and hence have to double estimations.<p>- jetbrains resharper for Web languages.