I found a demo cloak that was so nice I forgot to buy the product. It had "demo" written all over it, but the text was small, and from a distance it just looked like a pattern on the fabric. In fact, I got so used to the pattern I tuned it out until a friend pointed out, "um, you're still wearing a demo".
Dang, I should probably check and make sure I actually did buy the product. I've certainly got enough use out of that demo, the creator deserves something back for it.
Though I don't remember if the demo was free or not.