RenameWand

From Zach Scrivena:

Simple command-line utility for renaming files using an intuitive but powerful syntax (like regex, only much easier). Perform string operations (e.g. case conversions, rearrangements of substrings), arithmetic operations (e.g. on numbers in the filename), enumerate files (e.g. by name, size, time, or other attributes), and insert timestamps. Version 2.2 includes unspecified updates.