I'd like an autograph from either Frank Oz or Caroll Spinney because they are the ones carrying on the SS puppeteer legacy. If I got Frank's autograph, it would be awesome if he could sign as Miss Piggy, Fozzie, Sam, and Animal, too. If I got Caroll's autograph, I hope he'd add Big Bird and Oscar's signatures as well.
But if all of these puppeteers were alive, first I'd go for Jim (without question), then Frank, Jerry, Caroll, Dave, Richard, Steve, Kevin, & Bill in that order.