One significant productivity-enhancing feature that arrived with Tiger was Spotlight. On its own, it changed the way some (if not most) Mac users use their desktops. A simple command-space pops up the Spotlight window, where you can enter a query string, and in a matter of seconds, get a list of files matching your query.
Spotlight has many advantages over traditional file-searching tools. For one thing, it's not a tool. It is a complete indexing and search framework that is tightly integrated into the Operating System. In addition to filenames and paths, it also indexes by file metadata and content. So Spotlight returns query results based on what's inside the file.
Spotlight benefits can also be enjoyed on the commandline, and this article explains how you can take full advantage of it from inside the OS X Terminal window.
