Delete without harm? If you are rooted, any of the junk that the carrier put on. Anything Samsung/Android related will need to stay on your phone.

Why even do that? Get a Micro SD card for super cheap to add more storage to your phone. It has a micro sd card slot under the rear plastic case and above the battery location.

Or, backup all your unneeded music/videos/pictures to your computer and delete them from your phone.