Once again I had to copy a bunch of files into a folder that already contained some of those files. Once again I was struck by the weird user dialogue. I can select Yes, Yes to all, No, or cancel. What I need more than anything, is a No to all, but of course that option is not present.

According to a quick Google search, I am certainly not the first one to think this (no really a surprise) and some people even know of a way around this: the first time you select No, hold down the shift key and the No option will be used as the default for the rest of the copy action. If I can actually remember this it will save me a lot of aggravation.