College Coding project

For one of my next classes we have to develop a piece of software with a group, we get to propose our ideas to the teacher and my one requirement is that it be something useful.

So I figured I would throw out the question, what simple tool is your computer-life lacking? The limitations are Java and 5000+ lines of code. I have considered trying to do a re-build of code-bubbles IDE, or an Expert System as a coding aid.