Technically the Tanoshii Youchien and Otomodachi manga are lost media, though our pal
@MementoNepenthe has been doing a great job preserving them for us.
The Optimum dub is constantly on the verge of being lost media, and probably will be within the next decade.
There are plenty of commercials that are considered lost media. There are little to no recordings of YTV Promos.