You may not always have your optimal tool set, such as when you're remoting into someone else's environment (common for sysadmins or contractors), or when you're stuck using someone else's computer rather than your own.
It depends on what you do, I suppose. If your work doesn't have a large command-line component, using the command line might be disruptive.
A large part of my job involves working with remote Linux servers, so I chose to invest time learning Linux command line tools and vim. Now I'm more productive in a terminal than in a GUI environment. I use common tools that are installed by default on Linux/Unix/OSX, so I can sit down anywhere and do my work, or SSH directly into my machine and have my exact work environment securely and without latency.
Selecting a number of unrelated items from a list. Example: You have a folder with music files and want to select some to copy onto your portable music player. It's easier to click on the items to select them than typing all the names, even with file name completion.