I would suggest you not become involved in lame-o "pre-med" clubs.
If you really want to stand out, pick something you enjoy and GET INTO IT. People do various things, but a lot of people do the same type of stuff.
I can give you my personal story. I started out taking Tae Kwon Do and Karate when I began college. After a few years of this and studying the martial arts (studying, not taking) I tried different things: Aikido, Muay Thai, Wing Chun, and eventually stopped at Jeet Kune Do. I have sense become a serious student of JKD, studying not only the actual physical stuff but the intellectual stuff as well: biomechanics, fight dynamics, and the philosophy.
Originally I started because I wanted to beat people up. Then I settled into a "kindly protector" type role. The latter is still a reason why I do it, but I have become increasingly interested in the philosophy and dynamics of martial arts. This is my best and most unique EC, and I could easily weave this into a thousand different pro-Medical stories.
I help out with the youth at my church.
I am in Psi Chi, the Psych. Honor Society.
I play the saxophone, occasionally at a performance.
I am not currently doing it, but i have also volunteered at the hospital and shadowed a couple of times.
You will notice, I do not have a lot of EC's, but I have a lot to talk about for the few I have done. I forgot where I'm going with this, so I'll leave it at that.