When I was in CSS Security Support I used DebugDiag many times and I documented some of those cases here, such as:

This month we released a new version of DebugDiag. This version brings a new analysis engine converted to .NET, it has around 16 C# sample analysis rules and it allows you to write your own rules. A very powerful tool that just got better, go get it in the link below:

http://www.microsoft.com/en-us/download/details.aspx?id=40336