Being a writing-implement fanboy, I had to try out the new Sharpie Liquid Pencils, which are erasable for a few days and then become permanent. I’m not going to explain it much further, because they stink.
The form-factor is very much like a cheap uniball pen, except that you have to bear down quite noticeably in order to get a consistent line. The line created looks more like a black pen line than a pencil line, although it erases very well (I’ll give it that).
Much more expensive than a pencil, much less comfortable than a pen. Buy one only if you want to place it in your collection between New Coke and Crystal Pepsi.