Jason Polan, who you may remember from the series of drawings he did of every piece of art in the MoMA, has a unique 20x200 offering available. The larger editions are drawings and copies of his hand while the $2000 edition of 2 is described thusly:
I will come to your house and shake your hand. Two of these interactions will be available. After I meet you I will give you a certificate, to be signed by both you and me, stating the authentification of the encounter. This artwork is a collaboration between you and me. You will also receive a photograph that is taken the moment of our meeting.
20x200 curator Jen Bekman has more on this offering.
Jason's work is about a lot of lofty ideas, but those ideas are grounded in the most mundane of media and happenstance. The ideas center around his ambitions to interact authentically with both the media he chooses to work in and the collectors who buy his work.