I get the sentiment, but to be honest... after reviewing and deliberating on hundreds upon hundreds of applications each cycle, almost everyone blends in together, and nothing is truly unique in a positive way. Personally, I cannot recall any particular achievement that I would categorize as "unique".. Memorable, sure, but even then, I honestly can't tell you which of our applicants were the Rhodes or Fulbright scholars, former sport stars, or who set up a major national non-profit, led a symposium at a well-known international organization, or had a major authorship in a very high impact factor journal. These things all blend in together, have been done many times before, and do not automatically propel an applicant to the top.
"Superstars" by definition are impressive, but the vast majority of these applications are not unique. What they do have though is a consistent pattern of excellence, a good personality, a strong cohesive narrative, a breadth and depth of experiences that demonstrate their passion for *something*, and their ability to convey why these experiences will make them an excellent student, resident, and eventual colleague. Superstars just happen to do these things better than everyone else, and in doing so, create a memorable application despite each individual component not necessarily being that memorable.
So for those applying in the future: do pursue your passions, but don't fall into the mindset of needing to be "unique". The applicants who I remember as "unique" invariably are remembered for the wrong reasons. Just my humble thoughts.