This year I spend a lot of time working on an .NET ERP System with a bunch of nice colleagues. Wrote a couple of hundred unit tests, did dozens of code reviews and even more refactorings. My favorite and most used refactoring must be Refactoring Day 7 : Rename (method, class,parameter) in Pablo’s 31 days of Refactoring eBook.
http://www.lostechies.com/content/pablo_ebook.aspx (Download for free)