Assuming a song that doesn't already have one - Gypsy because of the story potential. A MTN part 2 experience with a return of the yellow brick road visual from that Applause performance
Favorite Gaga song among those where she self-references herself (i.e. includes "Gaga" in the lyrics): Just Dance, Bad Romance, Blood Mary, Government Hooker, Plastic Doll a few I can think of off the top of my head