A google search reveals that apparently, the Gun Club is a secret society founded by Earl Warren and friends and referenced in his autobiography.(See: http://alumni.berkeley.edu/news/california-magazine/fall-2012-politics-issue/warren-secrecy) The group is dedicated to drinking, poetry, and apparently smelling the roses.
It is also reported that white boards in the classrooms had GC symbols and the signature EW 14' (possibly indicating a mysterious 3L's initials or possibly because of the Club's apparent affiliation with the Chief and esteemed alumnus of the class of 1914).
Allegedly in the past the Club has been associated with such hi-jinks as planting love letters to Earl Warren and champagne in the study areas of the student center on valentine's day, hiring a look alike of the Dude from the Big Lebowski to give out drink tickets and silently promote the club at student activities fairs and plastering posters with Professor Yoo and the words "I'm sorry for everything" all over the school.
Who are these people and what do they want? Well, according to their poem they want the 1Ls to be kind and smell the roses...I'll drink to that.
Stay Berkeley, my friends.