I typically don't have much need for a renamer, but when I do, I just use Windows' built in renamer. If you grab a group of files, and click rename on one, it will rename the rest of the with (#).
On several occasions I created my own file renaming tools with MaxScript. What I liked best is that I could tell MaxScript to rename the file, then rename the file in SourceSafe/Perforce.
I used Ant Renamer for a while but haven't had a use for it in a while. http://www.antp.be/software/renamer/screenshots Renameit looks handy but most of what I rename are images and a lot of folders, so having a viewer/renamer is critical so I go with XnView. http://perso.orange.fr/pierre.g/xnview/enxnview.html
What utility do you guys use for batch-renaming lists of files in the WinOS these days? I used to use Rname-It, has a bunch of great tools but it doesn't support network drives. This one looks pretty good. http://sourceforge.net/projects/renameit/