What are some books that are very good, but had a limited print run, very unlikely to be reprinted, and thus worth a lot of money?

I was just thinking about this recently. So much stuff can be reprinted. Even if something's been out a long time there's usually a reprint at some point.
I have one book I own that seems to fit this criteria: The Book of the War edited by Lawrence Miles. Though you can get a .pdf. Maybe Charlee Jacob's Season of the Witch as well, but a hard to get book by her called Soma was just reprinted so maybe in the long rung Season of the Witch will be reprinted.

So what books do you own/know about that would fit what I'm talking about?