1) Quick console start. As rails developers, we spend way too much time waiting for consoles to start. This could save at least an hour out of my month.
2) Dynamically change production logging level. While their are ways to send signals to your process to control the logging level, this seems far more natural. You could easily open up an existing process change the logging level; finish your work; change it back.
Any other ideas for where the would be useful?