MD interviewers usually want to hear about my time as an interpreter at a free clinic. I didn’t do it for an insane number of hours or anything (only about 100) and I wouldn’t say free clinic experience is very unique either but interviewers always ask about it.
In terms of what stood out the most I dont think I had one super “unique” experience moreso than a bunch of little very interesting experiences (interpreted for legal teams helping refugees seek asylum, worked with an organization that helps run an advanced physics summer school in Palestine to increase access to biomedical research at Palestinian hospitals, edited several campus publications, was a camp counselor, won writing awards, etc).
What I thought would be my most major non-research EC, the >1000 hrs I put into a leadership position where I got a lot of pretty substantial stuff accomplished, has barely been brought up!!