Comic book fan here. I’ve got a paperback of the Batman: Contagion storyline autographed by several of the creators involved. I got Chris Claremont to autograph a copy of X-Men #1. I have a Peter David autographed Hulk comic. For some reason, Image comics sent me an autographed Spawn book. And I got author Jim Kruger to autograph my Earth X hardcover.
I have most of Chris Van Allsburg’s books signed. He lives in Providence and would come to a charity fund raiser every year to sign books and raise money for libraries. At the same event, I was able to get Natalie Babbitt to sign my copy of Tuck Everlasting (she’s a local author, too.) I also have a signed copy of Where the Wild Things Are.
Many years ago, Anne Rice was in town doing a signing, so I trotted out all the books I had by her and had them signed–she even signed the bondage books she wrote as A. N. Roqulaire.
Let’s see…
From Terry Pratchett, I have signed 1st Editions of Guards! Guards!, Carpe Jugulum, Hogfather, The Thief of Time, The Fifth Elephant, Nightwatch
From Larry Niven, I have signed 1st Editions of The Integral Trees, The Smoke Ring, Footfall (Jerry’s autograph, too.), Destiny’s Road, N-Space, The Gripping Hand (also with Jerry’s), Beowulf’s Children (signed by all three authors , and my pride and joy, a signed 1st Edition of Ringworld , with the mistakes in it.
Virtually everything Harlan Ellison has published.
Several by Harry Turtledove and S. M. Sterling.
Most of George R. R. Martin’s books.
A few others. I tend to only get signed copies from the authors I enjoy talking to.
My daughter has a signed, first edition of the original Harry Potter book. Her dad picked it up for her when he was in England about 10 years ago. There was a little bit of a buzz starting about the book, and it was recommended to him as something a 8-year-old might enjoy. So he went to a bookstore and Rowling happened to be there promoting it.
I keep telling her that she can sell it to pay for her college tuition if the scholarships fall through.
Ummm, Capri? A true first of the 1st Harry Potter - hardback with no dust jacket - goes for $25,000 US unsigned and likely several $thousand more signed. You really need to a) research that it is a true first - easy to do on line via eBay, bookfinder.com and any number of Harry sites - be very careful, true 1st are tricky and you really need to do your research - I don’t want to disappoint, but it is likely not a true first - still potentially quite pricey, but not $25K or more; b) if you suspect it is a true first based on your research, take it to a dealer and get it appraised for insurance purposes (you can email me and let me know where in general you live - I may know of some dealers I can recommend); and c) get it insured.
This ain’t no foolin’ around.
Dalva, by Jim Harrison (also wrote Legends of the Fall). I met him at my friend’s wedding in Montana, but he came to Tallahassee last year to do a reading, so I took my copy of the only book of his I had and asked him to sign it.
I also met Peter Matheisson there, but didn’t own any of his works at the time.
My friend’s husband is also an author, Doug Peacock, but it seemed weird to ask him to sign his book when I was there for his wedding, not to be his literary groupie.
And then, of course, my friend’s book: Libby, Montana: Asbestos and the Deadly Silence of an American Corporation, by Andrea Peacock. I helped her edit early versions of it, so naturally she gave me a signed copy.
I checked out a copy of Fury, by Salman Rushdie from the library and saw that it was signed. Pretty cool.
The Intelligent Woman’s Guide to Socialism and Capitalism by George Bernard Shaw
The Rosewood Coffin by Sharyn McCrumb
and J.D. Robb (actually Nora Roberts) signed a short story anthology for me.
I gave up soliciting autographs many years ago when I decided that standing in line to get a signature that was nothing I would care about the next day was a waste of my time. Just a personal decision. I understand most other people feel differently.
I do have many writer friends so I get them to inscribe their books to have a personal remembrance. None of them would mean anything to outsiders, but my favorite is on Harlan Ellison’s very appropriately titled “Over the Edge”
Yes, there’s a story behind that…
A copy of Crispin Glover’s Rat Catching. I met him at a Comic book convention last year (I’m not a comic book person, I was there to see a friend of mine’s film.) He seemed as puzzled by the people in costumes as I was.
Oddly enough, most of the books I’ve gotten autographed were not for me. I got a first-edition Monstrous Regiment for one of my best friends and a copy of Everything You Know Is Wrong for my mother.
For myself, I have a copy of The Beggar Queen by Lloyd Alexander, a rather old paperback of Flowers in the Attic, and a copy of the Complete Works of William Shakespeare signed by…well, signed by Pterry signing as Wm. Shaksberd. 
Another collector and dealer here. I have a fairly small number of books that I will not be selling.
I have all of the Iain Pears British firsts signed by him.
I have a large collection of items relating to the culture and history of Haiti signed, including the signature of former President Jean Bertrand Aristide. Julia Alvarez signed a copy of “Yo” for me at a reading.
Tim O’Brien signed a paperback of the Nuclear Age.
A Richard Burton (explorer not actor) biography signed by his niece.
The signed items I have sold are much more fun. In the past I have sold books signed by:
Gabriel Garcia Marquez
Norman MacLean
Richard Burton
Ambrose Bierce
Zora Neale Hurston
A single page of a handwritten play by the Marquis de Sade written in prison
Kazuo Ishiguro
Plus many documents or inscribed books by explorers of the eighteenth and nineteenth century that no one remembers anymore.
It is painful to be too poor to keep the really good stuff.
These are the ones where I asked for an autograph:
Empire signed by both Howard Chaykin and Samuel R. Delany
Rite of Passage, Alexi Panshin
These came to me autographed:
Swashbuckling Editor Stories, ed. by John Betancourt, leatherbound hardcover edition, double lettered, with autographs of all contributors. I see bookstores are selling this edition for $90; only 16 copies of this edition (there were several others) were produced and they were never offered for sale.
The Pleistoscene Redemption by Dan Gallagher (but everyone has those)
Picoverse by Robert A. Metzger
Dance for the Ivory Madonna by Don A. Sakers
I believe my copies of James Morrow’s Only Begotten Daughter and Towing Jehovah are autographed, but I’ll have to double check.
Many others. I get one or two autographed copies of books mailed to me unsolicited each year.
I got David Sedaris to sign my copy of Me Talk Pretty One Day in October. I also own a copy of The Tiny Warrior by D. J. “Eagle Bear” Vanas, one of my aunt’s former students. It actally has a pretty length inscription in it.
My mom gave me some children’s books when I was younger that were autographed, but I don’t remember which ones. Nothing big like Goodnight, Moon, though.
Well, a few over the years
Ken Kesey’s Sometimes a Great Notion
Arthur C. Clarke Childhood’s End signed in early 1968 when he visited our small U.S. university. This was before we had heard about the movie 2001, and he had some advance publicity stills to show us. Wow!
Ursula K. LeGuin’s Earthsea Trilogy
Jack Chalker’s Dance Band on the Titanic
Kevin O’Donnell, Jr.'s Bandersnatch and Fire on the Border. The latter, an advance reader’s copy, was mailed to me with a nice note from Mr. O’Donnell after we met at a Westercon, thereby hugely increasing my cool quotient at the newspaper where I work
T. Jackson King’s Retread Shop, a highly recommended coming-of-age SF adventure.
And a number of regional authors whose work I admire.
The only signed book I have is a copy of “Who Stole Feminism?” by Christna Hoff Sommers.
I have a bunch of poetry:
Triggering Towns by Richard Hugo
Lady in Kicking Horse Reservoir by Richard Hugo
Road Ends at Tahola by Richard Hugo
Radiation by Sandra McPherson
The Zimmer Poems by Paul Zimmer
Tunes for Bears to Dance to by** Ronald Wallace**
The Dolphin by Robert Lowell (very damaged)
Looking for Holes in the Ceiling by Stephen Dunn
and
Tehanu by Ursula LeGuin
I used to manage a bookstore so I also have some oddball ones that I can’t remember why I have, like:
First Lady from Plains by Rosalynn Carter
Sudden Death by Rita Mae Brown
Clan of the Cave Bear by Jean Auel (paperback)
The Stranger Beside Me by Anne Rule (paperback)
I have many. My favorites are the complete works of Andrew Vachss, my signed copy of Assignment in Eternity, by Robert A. Heinlein, and the two Howard Stern books, Private Parts and Miss America.
I also have many signed CD’s and albums from comedians ranging from Slappy White to Sam Kinison.
I have Hedwig and the Angry Inch by the one, the only, the “I’m not worthy!” - John Cameron Mitchell. He also signed the cast on my leg - he’s such a dear!
I go hobbling around telling people: “Look! JCM signed my cast!” and they all go “WHO?”
I have an autographed hardcover of Jean Auel’s The Plains of Passage. The worst volume in the series, IMHO.