My favorite PyCon talk comes from, who else, Raymond Hettinger at PyCon US 2013 and is titled Transforming Code into Beautiful, Idiomatic Python.
I had been a Python developer for maybe a year-and-half at this point and was starting to grok some more advanced concepts. But, I remember walking out of that talk thinking about how excited Raymond was about Python and how to make Python code beautiful. I'm sure I've forgotten a few, but most everything I learned about in that talk (like context managers, looping over dictionary key/value pairs, counting with dictionaries, and decorators) have all really stuck with me and influenced how I tackle problems.