My favorite material to use in jewelry-making is pocket watches -- all parts of them, any shape, any size, any condition (though I do not like to disassemble watches that could be repaired).
After having sold a few items of this style, I consider it my signature piece. The pic on the bottom left shows how I made the back of a few of the pendants. A couple had the original smooth watch back plate, but I think the internal plate lent more interest to the work. The one on the upper left is for sale in my ArtFire shop; just click and buy! =)