Alpha Omega Alpha...like Phi Beta Kappa except residency directors at top programs (read: surgery) actually care alot about whether you're a member. Some schools don't have AOA chapters though, which is nice/one less thing to do.
I have but the most noble intentions for demonstrated peer leadership or weekend volunteerism, and would never imply such a thing
Seriously though, a lot of the pre-med process is just jumping through hoops because it's a buyer's market (for schools) right now. If med schools experience an a la law school crisis, you can bet 99% of the stuff required now and even GPA/MCAT would become much less relevant.