py-bugger
People typically have to learn debugging by focusing on whatever bug happens to come up in their development work. People don't usually get the chance to progress from simple to more complex bugs.
py-bugger lets you intentionally introduce specific kinds of bugs to a working project. You can introduce bugs to a single .py file, or a fully-developed project. This is much different from the typical process of waiting for your next bug to show up, or introducing a bug yourself.
py-bugger gives people a structured way to learn debugging, just as we approach most other areas of programming.