Cargo Cult Science (Click for the .pdf) by Richard P. Feynman. Some remarks on science, pseudoscience and learning not to fool yourself. Caltech’s 1974 commmencement address. (Originally from Caltech library website, now hosted on WordPress.com)
The scientist that I most look up to is the late Professor Richard P. Feynman. The man did everything and looked good doing it. Amongst these things he: was awarded a Nobel prize for work in quantum electrodynamics; worked on the Manhattan project and was the only person to see the nuclear explosion with naked eyes; cracked safes containing national secrets while working at Los Alamos (for fun); was chief investigator to the Challenger explosion in 1986 and explained why the space shuttle blew up using a rubber o-ring and a bowl of cold water; was a great teacher; and is still revered today for all these things.
Richard Feynman was a fantastic scientist and populariser of science (these things do not always [in fact, rarely] go together). I have attached to this post one of his speeches which encapsulates both of these aspects. Just a clear succinct message that emphasises what makes science the best way to find something out about the world. It contains exceedingly simple points that many scientists today actually don’t follow, and so I think it should be required reading for any scientist. But even if you aren’t, I hope you read it anyway because it really is quite a nice speech.