I am particularly curious about the distributed pair programming plugin. I've always wondered what other ways there are to pair program besides sharing 1 keyboard. It seems like it could be a good productivity tool even if you're in the same office.
I'll also list my favorite Eclipse plugins, prior to reading the above. I'm somewhat surprised none of them are on the list.
- Findbugs plugin (less useful once you have Continuous Integration that reports this, but still cool)
- EclEmma (Code coverage highlighting in Eclipse with an Emma junit test runner)
- SwingExplorer - very sweet way to delve through swing code and familiarize yourself with the GUI code in a project
For more plugin ideas, you may want to read this StackOverflow question.
What Eclipse plugins do you use?