Great thread.
Like Bob, the E121 Ruth would be on my list.
But the other items in the running would include.
- T3 Mathewson or Cobb.
- Type 1 Conlon Photos (Shoeless Joe, Babe Ruth, Ty Cobb, Gehrig)
I view Conlon photos as the baseball equivalent of Ansel Adams. As a collector, they just stand out but I also think that over time they'll gain greater appreciation.