Drizzt Books.
I have a couple of original cover books, all of the lockwood cover in a5 paperback and I'm going to get the large hardcovers once I'm making money. (Fulltime student here.)
Also Games, I've got the collectors editions of just about every game I've cared about that's been released since 2008. Also the collectors of Gears of War. I don't care about gears but the collectors was and extra 10 bucks so like... why not.
My girlfriend and I like to own entire DVD box sets, we have Scrubs, How I Met Your Mother, One Tree Hill, Brothers and Sisters, Deadwood, The Big Bang Theory, we're working on Avatar the Last Airbender.
I also like books in general. I have all of the Harry Potter books in hard cover original run prints except the first, which apparently was never released as a hardcover in the original run.

I think it's a lie. We also have some nice older books. Like "The Wrath of Grapes" it's so old that I swear it was printed on an old school printing press.
I use to keep all of my bus tickets... I had at least 5 a week. This went on for about a year.
So really nothing especially valuable or rare. I mean, most of it cannot be replaced, so it's technically valuable, but we couldn't sell any of it for excessive money unless we managed to find someone looking to replace lost or stolen items.