don't do it a lot but have had some luck... I don't have access to photos so send a small card but most send back photos
T.J. Thyne (along with a personal not, I asked him to have Fox stop moving the damn show around so much)..
John Francis Daley
Duckey NCIS (got it for my father who loves the show)
Sent Amber Lancaster an index card and she sent THREE photos back (sent to price is right)
Few non TTM
Emma Caulfield in a bunny outfit (buffy reference) donated to her kickstarter
And finally my prized auto (got in person)
Took my father to a Hillary rally in 08 hosted by Bill Clinton, he took time to talk to my father (who is in a wheel chair) and signed and gave him this hat.