For me, it would have to be my original
DM's screen. I
DM'ed the same group of guys through junior high and high school, through a ton of adventures over countless weekends and I used same screens for it all.
About a year ago, a couple of these old friends and I played again for the first time in about a decade. They lugged their books to my place and we stared setting up at the dinner table. I put the screens up and they gave me this odd look. "Dude, the screens are backward - that one has to be facing me."
I dug that.