I recently had the need to create an image so that when a user bookmarks a site on their smartphone and adds that bookmark to their home screen, an icon appears. Scott Sawyer has an excellent post detailing the setup to add this image to your Drupal 7 site. I recommend checking it out.
Let's say that you are building out a "Person" content type that will contain several hundred people. Each person can optionally be tagged as an expert in one of several categories. Your "Person" content type fields might look something like this:
The site that you're building requires that you show just the experts out of the entire set of People nodes. Easy, right?
Drush is certainly a tool that makes Drupal development faster. Even with that speed, I found myself typing the same commands over and over again every morning just to get started, and I wanted to cut down on that time. We use two repositories at Princeton, one for core and sites/all, and one for the sites/sitename folder. So, I had to update two repos (git pull), update the database just in case (drush updatedb), clear cache (drush cc all), and switch between directories to do so.
The design for pace.princeton.edu called for a banner image that could be on a third level page and every page below it. For example, in the Community House section of the site, the banner remains consistent. When the Pace Center adds a new page under the Community House page, it automatically gets the Community House banner.