try this MacPrince, I found it on another site:
To remove ringtones from the ringtones tab in iTunes, first delete the ringtones from the "ringtones" folder in the finder, then rebuild your iTunes database according to http://docs.info.apple.com/article.html?artnum=93313
Thanks, I needed that too. And yes the ringtones sync again w/ .m4a extension, but you now have to place them in the folder instead of just double clicking them.