Name Mangler is a batch file renaming tool. A simple and intuitive interface makes it easy for you to rename hundreds or thousands of files at a time.
Basic use requires nothing more than choosing the files to rename, and then picking (from a pop-up menu) the type of changes to make: Find and Replace, Number Sequentially, Change Case, Add Prefix/Suffix, etc. An Advanced mode allows users to string together renaming commands to apply more than one operation per renaming activity.
In Name Mangler's interface, you'll see a "before and after" preview of the renaming task, so you can verify that what you think is going to happen is what's going to happen. You can even see previews of the content of files and images in a Quick Look window, just to make sure you've got the right files selected.
If you have a renaming task you do regularly, you can create a droplet, which is a small standalone application that stores a particular renaming task.