Dungeons and Dragons 3.5 module published by AEG in 2005. 800 pages, 1600 rooms, 5lb tome. It had just come out, so I took it to GenCon and got as many signatures as I could. Posi, Arctic Sun, Cricket, States, Dr. Vahz, and many players signed it, in addition to a ton of other friends, including the staff of Bioware, Catalyst Game Labs, artists, pirates, everyone I could find that I knew.
People have since called it the Gaming Necronomicon and denied it exists, heh. Tre hung out with me, Kelp Plankton, and Pouncetta all week.
I will also note that GenCon is when I got his number, so we could keep in touch. That later lead to the (in)famous real life phone call in character to get him online when Ghost Widow logged in before CoV's release, asking for him. I was the character trying to get them to go out on a date.