I have quite a few items covered in clay. I believe the first thing I made was a clay covered pen. I was a little surprised that you could put the plastic pen barrel (but NOT the ink cartridge!) in the oven. As with most things, I had to go all out with my clay covered pens. I've made moose, cat, dog, penguin, gnome pens, and more. They're as much decorative as they are utilitarian. You can look at them and never even know it's actually a pen.
Lately I've discovered the fun of covering metal boxes and tins in clay. This started as a way to recycle my flavored coffee tins. They're the perfect size to hold small treasures and things you want to keep on hand. These are also pretty enough to be used as decoration. I've been covering mint and candy tins with polymer clay as well. I've always used the tins to store things in anyway- why not make the tins more attractive? I'm enjoying finding different ways to re-make these objects. I even incorporated beading into one of my tins. They're the perfect size to try new techniques on- small enough not to be intimidating, yet large enough to get a feel for the technique.
I'm sure I'll continue experimenting and finding new ways to cover objects in clay.