Lisp Hackers: Peter Seibel
Funny - when looking at a codebase for the first time, I do almost exactly the same thing as described by Mr Seibel: I start rewriting it. I rename functions or methods that I think have poorly chosen names, I rename the names of fields, variables or parameters for the same reason, I refactor, restructure, and reformat the code to look like I think it should look, and so on.