Last week I found myself creating a custom work item and needed to add a few new fields to TFS. That wasn't anything special in itself, but when I decided to change the names of my new fields (I'm blonde after all), things became more interesting. It turns out that TFS can only have one field for a specific friendly name. That sounds obvious, but when we also provide a "ReferenceName" that has a distinct namespace feel about it, I thought I could get away with it. Wrong!
Fortunately there's a neat tool that ships with TFS to rename fields (and other stuff). Check out witfields.exe. You won't use it all that often, but it's good to know it's there.