If you don't want a standard autographed 8x10, you could get him to sign an ice cold can of Miller Light:
The quickly down the can of beer and crush it against your head.
Or, if you don't like beer, you can get him to sign a box of Chicken in a Biskit:
Then quickly eat all the crackers and crush the box against your head.
How about bring a Carvel Cookie Puss with you and then having Dana sign it in icing!
The quickly eat the Cookie Puss and get a MAJOR ice cream headache... causing you feel like you smashed something against your head.
You could get Dana to sign a picture of THE OTHER DANA SNYDER from Shawshank Redemption:
Have Dana write something about how he played the 1954 Food Way Woman and was a woman with female parts. That'd be hot.
Or just have him sign your Slapsy Maxie Rosenbloom Co-Stars record:
If none of these work, maybe he can just draw an executive coaster for you:
Plus! At Supercon you can meet all your favorite celebrities and George Takei.