As the resident TFS admin, on occasion I am asked to undo a checkout (usually a lock) that a user has on a certain file. This can be done via the command line using the TF.e
Command line
tf undo /workspace: OtherUserWorkspace;OtherUser $/TeamProject/MyFile.cs /s:http://YourTFSServer:8080
https://msdn.microsoft.com/en-us/library/cc470668.aspx