Team Foundation Server
After Chris demonstrated each component of TFS, I didn't any particular piece overly exciting. For example, I didn't see anything the source control component could do that subversion couldn't. Nor was the bug tracker particularly impressive. The real selling point is the integration of components. Most developers have a bug tracker, most have source control, and some even have a documentation system in place, but almost no one has an integrated solution. That's the true power of TFS. With everything integrated, you can easily control the software development process and micromanage your team to hell!