Creative uses for time machines

There are a few standard things to do with a time machine:

• Kill people (like Hitler).
• Prevent people from getting killed (like JFK).
• Make a killing on the stock market or sports betting.
• Lord it over ancient peoples with modern technology.
• Bring future technology (like a cure for cancer) back to the present.
• Prevent an ugly breakup.
• Become your own grandfather.
• Stop another time traveler from screwing something up.

But a time machine is a powerful thing. Can you think of some more surprising uses?

For example, I think I would most appreciate a time machine as a tool for experimental psychology. In physics and chemistry (and, to a lesser extent, biology), experimentation is straightforward: you can usually set up identical conditions for testing with different interventions. In psychology, on the other hand, you can't cook up a batch of humans to precise specifications in the laboratory, and once you've done one thing to a human subject, you can't wholly undo it before trying something else. With a time machine, though, you could try something, observe the results, go back in time, and try something else. You could thus see the pure effect of your interventions directly, since you'd know that literally nothing distinguished the experimental conditions other than what you did.