As a web developer I'm constantly working on projects in different environments (local, staging, testing, production). I mostly work on Drupal projects. I can't tell you the number of times I've been led from local to production by just browsing the site. And then accidentally changing a setting on production that was really only supposed to be changed on my local environment.
So here's an idea: A Chrome theme that changes color depending on the sub domain of a site.
For example: on local.mysite.com* the browser chrome should be green, on staging.mysite.com* it should be blue, and on mysite.com* the color should be standard chrome grey.
This could avoid a lot of confusion for a lot of people working in different environments. Not only for developers, also for "content" people.
Sadly, I have no idea how to code a Chrome theme with that kind of behavior.