Git is far and away the best revision control system I've ever used. As evidence, I submit this little gem of a command:

repo$ git update-index --assume-unchanged file1 file2 ...

This is a useful command to use when you want to change a file locally and prevent it from being committed back to the repository. Once you're done and want to re-enable commits of those files, simply re-run the command and use --no-assume-unchanged.