a signed copy of the draco and the malfoy's CD Party Like You're Evil...
It's a CD by fans... and I treasure it.
Also... A life sized cardboard cut-out of Jack Sparrow and also the 4 different forms of J'onn J'onz Martian Manhunter from Justice League the animated series in action figure form :)
then mine is probably a photo of harry and the potters and me at the order of the phoenix book release at borders in boston in 2003 (their first public concert!) that i had them sign when i went to the yule ball last year :)