As I have asked on StackOverflow (http://stackoverflow.com/questions/2818082/how-to-diff-two-regions-of-the-same-file-in-eclipse) there is an open window for a diff tool that can diff regions even in the same file.
Usecase is refactoring out similar code especially if you are using a refactoring tool that can do it automatically. Often the code is not the same initially (unless you just C&P:ed it, and then there are tools that can identify the copies), but you need to see if the sections can be made more similar. Here a good tool to visualize differences are essential. But all diff-tools that I have seen focus on differences between files.
I want a tool that focuses on regions, even inside the same file.