Silver Surfer would be my choice. After reading the book, "Marvel Comics, the Untold Story", I think he really enjoyed writing that. Some great covers there, issue four and the issue with Mephisto come to mind.
Regarding value and price appreciation, I'm not sure if I would pay (is it $100?) to have him sign something for appreciation. He's signed many books. I would check ebay and see what's going on with the pricing. You might be able to get a better book signed and not have to hassle with the certification, etc. I was just reading in the Desert Wind post someone got an ASM 50 double signed with Lee and Romita. That looked sweet.